[meta-darwin] Patch GCC for aarch64 macOS host build on aarch64 linux host

From: "Eric L. Hernes" <eric@qinc.tv>

The configure script and aarch64.h get a bit confused when building
the darwin cross canadian.  `driver-aarch64.c` gets added which has
more build problems and isn't needed on the cross build.  The
`aarch64.h` file looks for `sysctl/..h` headers when targeting MACHO
binaries , which also do not exist on the linux build machine.

There should be a CPP macro for "linux_build_host" or
similar to use for the system dependent includes and config.  Since we
don't have this, we use (!defined(darwin_macosx_version_min)), which
seems to be "darwin builds only".  It's a bit of a hack, but should be
ok for this deep corner case.

Without this patch, cross builds targeting macOS/arm64 on a Linux
Intel machine work; but linux arm64 does not.  This is maybe a more
common situation. With Apple Intel machines out of production for 5+
years now, Docker on Apple Silicon should be much more common, and
getting more so.

It is possible to configure an Intel Docker image on Apple Silicon
with Rosetta 2, but the builds with native arm64 are significantly
faster.

commit da00745de4531722df9b955892c5835a7c26c03f
Author: Eric L. Hernes <dev@qinc.tv>
Signed-off-by: Eric L. Hernes <dev@qinc.tv>
Date:   Mon Jan 19 09:54:57 2026 -0600

    additional patch for gcc to build on arm64 build for arm64 host
---
 .../gcc/files/0102-aarch64-on-aarch64.patch   | 32 +++++++++++++++++++
 recipes-devtools/gcc/gcc-source_%.bbappend    |  4 +++
 2 files changed, 36 insertions(+)
 create mode 100644 recipes-devtools/gcc/files/0102-aarch64-on-aarch64.patch

Hi Eric,
thanks for the patch! I have merged it upstream as
https://git.yoctoproject.org/meta-darwin/commit/?id=2ddb2d2c52e9b0cdc6bdf57b001aa6eef23f6fef
. I have only removed those lines from the commit message. I've assumed
they were not intentional:

```
commit da00745de4531722df9b955892c5835a7c26c03f
Author: Eric L. Hernes <dev@qinc.tv>
Date:   Mon Jan 19 09:54:57 2026 -0600

    additional patch for gcc to build on arm64 build for arm64 host
```

Étienne

On Wed, Jan 28, 2026 at 7:30 AM Eric L. Hernes via lists.yoctoproject.org
<dev=qinc.tv@lists.yoctoproject.org> wrote:

> From: "Eric L. Hernes" <eric@qinc.tv>
>
> The configure script and aarch64.h get a bit confused when building
> the darwin cross canadian.  `driver-aarch64.c` gets added which has
> more build problems and isn't needed on the cross build.  The
> `aarch64.h` file looks for `sysctl/..h` headers when targeting MACHO
> binaries , which also do not exist on the linux build machine.
>
> There should be a CPP macro for "linux_build_host" or
> similar to use for the system dependent includes and config.  Since we
> don't have this, we use (!defined(darwin_macosx_version_min)), which
> seems to be "darwin builds only".  It's a bit of a hack, but should be
> ok for this deep corner case.
>
> Without this patch, cross builds targeting macOS/arm64 on a Linux
> Intel machine work; but linux arm64 does not.  This is maybe a more
> common situation. With Apple Intel machines out of production for 5+
> years now, Docker on Apple Silicon should be much more common, and
> getting more so.
>
> It is possible to configure an Intel Docker image on Apple Silicon
> with Rosetta 2, but the builds with native arm64 are significantly
> faster.
>
> commit da00745de4531722df9b955892c5835a7c26c03f
> Author: Eric L. Hernes <dev@qinc.tv>
> Signed-off-by: Eric L. Hernes <dev@qinc.tv>
> Date:   Mon Jan 19 09:54:57 2026 -0600
>
>     additional patch for gcc to build on arm64 build for arm64 host
> ---
>  .../gcc/files/0102-aarch64-on-aarch64.patch   | 32 +++++++++++++++++++
>  recipes-devtools/gcc/gcc-source_%.bbappend    |  4 +++
>  2 files changed, 36 insertions(+)
>  create mode 100644
> recipes-devtools/gcc/files/0102-aarch64-on-aarch64.patch
>
> diff --git a/recipes-devtools/gcc/files/0102-aarch64-on-aarch64.patch
> b/recipes-devtools/gcc/files/0102-aarch64-on-aarch64.patch
> new file mode 100644
> index 0000000..f6da25f
> --- /dev/null
> +++ b/recipes-devtools/gcc/files/0102-aarch64-on-aarch64.patch
> @@ -0,0 +1,32 @@
> +Upstream-Status: Inappropriate [OE specific]
> +Signed-off-by: Eric L. Hernes <dev@qinc.tv>
> +--- gcc-13.4.0/gcc/config.host~        2026-01-08 23:01:47.056268010 +0000
> ++++ gcc-13.4.0/gcc/config.host 2026-01-08 23:10:07.958588006 +0000
> +@@ -102,6 +102,9 @@
> +   aarch64*-*-freebsd* | aarch64*-*-linux* | aarch64*-*-fuchsia* |\
> +   aarch64*-*-darwin*)
> +     case ${target} in
> ++      *-oesdk-*)
> ++      # don't add driver-aarch64.o for oesdk cross builds
> ++      ;;
> +       aarch64*-*-*)
> +       host_extra_gcc_objs="driver-aarch64.o"
> +       host_xmake_file="${host_xmake_file} aarch64/x-aarch64"
> +--- gcc-13.4.0/gcc/config/aarch64/aarch64.h~   2026-01-08
> 23:01:46.859268010 +0000
> ++++ gcc-13.4.0/gcc/config/aarch64/aarch64.h    2026-01-08
> 23:08:14.417236009 +0000
> +@@ -1223,7 +1223,14 @@
> +
> + /* Extra specs when building a native AArch64-hosted compiler.
> +    Option rewriting rules based on host system.  */
> +-#if defined(__aarch64__)
> ++
> ++//
> ++// XXX-ELH: we don't do this for crosssdk builds,
> ++// so how do we know that? For now we just pick a symbol that is defined
> in the build
> ++//
> ++// g++ -fno-PIE -dM -E  .....  -MT gcc.o -MMD -MP -MF ./.deps/gcc.TPo
> ../../../../../../../work-shared/gcc-13.4.0-r0/gcc-13.4.0/gcc/gcc.cc
> ++//
> ++#if defined(__aarch64__) && !defined(darwin_macosx_version_min)
> + extern const char *host_detect_local_cpu (int argc, const char **argv);
> + #define HAVE_LOCAL_CPU_DETECT
> + # define EXTRA_SPEC_FUNCTIONS                                           \
> diff --git a/recipes-devtools/gcc/gcc-source_%.bbappend
> b/recipes-devtools/gcc/gcc-source_%.bbappend
> index 73b4843..d1089e5 100644
> --- a/recipes-devtools/gcc/gcc-source_%.bbappend
> +++ b/recipes-devtools/gcc/gcc-source_%.bbappend
> @@ -9,3 +9,7 @@ SRC_URI:append = " \
>  SRC_URI:append = " \
>      file://0101-aarch64-Darwin-support-gcc-13-darwin.patch \
>  "
> +# Patch to allow building aarch64 toolchain for mac on aarch64 linux
> +SRC_URI:append = " \
> +    file://0102-aarch64-on-aarch64.patch \
> +"
> --
> 2.50.1 (Apple Git-155)
>
>
>
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