boost: Allow building with GCC on macOS (#24895)

var/spack/repos/builtin/packages/boost/context-macho-gcc.patch

@@ -0,0 +1,22 @@
+diff --git a/build/Jamfile.v2 b/build/Jamfile.v2
+index eb83bbb..8d8dac8 100644
+--- a/libs/context/build/Jamfile.v2
++++ b/libs/context/build/Jamfile.v2
+@@ -646,6 +646,17 @@ alias asm_sources
+      <toolset>clang
+    ;
+
++alias asm_sources
++   : asm/make_x86_64_sysv_macho_gas.S
++     asm/jump_x86_64_sysv_macho_gas.S
++     asm/ontop_x86_64_sysv_macho_gas.S
++   : <abi>sysv
++     <address-model>64
++     <architecture>x86
++     <binary-format>mach-o
++     <toolset>gcc
++   ;
++
+ alias asm_sources
+    : asm/make_x86_64_sysv_macho_gas.S
+      asm/jump_x86_64_sysv_macho_gas.S

var/spack/repos/builtin/packages/boost/package.py

@@ -277,6 +277,11 @@ def libs(self):
     # and https://github.com/spack/spack/pull/21408
     patch("bootstrap-toolset.patch", when="@1.75")
 
+    # Allow building context asm sources with GCC on Darwin
+    # See https://github.com/spack/spack/pull/24889
+    # and https://github.com/boostorg/context/issues/177
+    patch("context-macho-gcc.patch", when="+context platform=darwin %gcc")
+
     def patch(self):
         # Disable SSSE3 and AVX2 when using the NVIDIA compiler
         if self.spec.satisfies('%nvhpc'):