tests/tcg: add alternative cross-compilers for macos (homebrew)

Add support for cross compilers that can be installed with
homebrew: https://github.com/orgs/Homebrew/packages?tab=packages&q=-gcc
- i686-elf-gcc
- x86_64-elf-gcc
- aarch64-elf-gcc
- m68k-elf-gcc (ignored since we don't have system tests for m68k)
- riscv64-elf-gcc
- arm-none-eabi-gcc

Those toolchain target bare metal, so can be used for softmmu targets
only (macos has no user target anyway).

With this, we can also cleanup our CI for MacOS since it does not
require any --cross-prefix anymore.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20260924213942.26491-5-pierrick.bouvier@oss.qualcomm.com
Signed-off-by: Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com>

.gitlab-ci.d/macos.yml

@@ -41,10 +41,6 @@ aarch64-macos-15-build:
     PKG_CONFIG_PATH: /opt/homebrew/curl/lib/pkgconfig:/opt/homebrew/ncurses/lib/pkgconfig:/opt/homebrew/readline/lib/pkgconfig
     CONFIGURE_ARGS:
         --target-list=aarch64-softmmu,arm-softmmu,i386-softmmu,x86_64-softmmu
-        --cross-prefix-aarch64=aarch64-elf-
-        --cross-prefix-arm=arm-none-eabi-
-        --cross-prefix-i386=i686-elf-
-        --cross-prefix-x86_64=x86_64-elf-
         --disable-plugins
     TEST_TARGETS: check-unit check-tcg
 
@@ -59,8 +55,5 @@ aarch64-macos-26-build:
     PKG_CONFIG_PATH: /opt/homebrew/curl/lib/pkgconfig:/opt/homebrew/ncurses/lib/pkgconfig:/opt/homebrew/readline/lib/pkgconfig
     CONFIGURE_ARGS:
         --target-list=aarch64-softmmu,i386-softmmu,x86_64-softmmu
-        --cross-prefix-aarch64=aarch64-elf-
-        --cross-prefix-i386=i686-elf-
-        --cross-prefix-x86_64=x86_64-elf-
         --disable-plugins
     TEST_TARGETS: check-unit check-tcg

tests/tcg/aarch64/system/meson.build

@@ -96,7 +96,7 @@ if 'qemu-system-aarch64' in emulators
   tcg_tests += {
     'aarch64-softmmu': {
       'cc': cc,
-      'cc_alt': cc_alt,
+      'cc_alt': cc_alt + ['aarch64-elf-gcc'],
       'cc_dockerfile': cc_dockerfile,
       'cc_feat_cflags': cc_feat_cflags,
       'folder': 'aarch64/system',

tests/tcg/arm/system/meson.build

@@ -64,6 +64,7 @@ if 'qemu-system-arm' in emulators
   tcg_tests += {
     'arm-softmmu': {
       'cc': cc,
+      'cc_alt': ['arm-none-eabi-gcc'],
       'cc_dockerfile': cc_dockerfile,
       'folder': 'arm/system',
       'gdb_arch': 'arm',

tests/tcg/i386/system/meson.build

@@ -42,6 +42,7 @@ if 'qemu-system-i386' in emulators
   tcg_tests += {
     'i386-softmmu': {
       'cc': cc,
+      'cc_alt': ['i686-elf-gcc'],
       'cc_dockerfile': cc_dockerfile,
       'folder': 'i386/system',
       'gdb_arch': 'i386',

tests/tcg/riscv64/system/meson.build

@@ -65,7 +65,7 @@ if 'qemu-system-riscv64' in emulators
   tcg_tests += {
     'riscv64-softmmu': {
       'cc': cc,
-      'cc_alt': cc_alt,
+      'cc_alt': cc_alt + ['riscv64-elf-gcc'],
       'cc_dockerfile': cc_dockerfile,
       'folder': 'riscv64',
       'gdb_arch': 'riscv64',

tests/tcg/x86_64/system/meson.build

@@ -52,7 +52,7 @@ if 'qemu-system-x86_64' in emulators
   tcg_tests += {
     'x86_64-softmmu': {
       'cc': cc,
-      'cc_alt': cc_alt,
+      'cc_alt': cc_alt + ['x86_64-elf-gcc'],
       'cc_dockerfile': cc_dockerfile,
       'folder': 'x86_64/system',
       'gdb_arch': 'x86_64',