gcc15: fix build on aarch64-darwin

This fixes the GCC 15.2.0 build on aarch64-darwin by addressing two issues
in the libgcc build process:

1. Update libgcc-darwin-detection.patch:
- Catch arm64-apple-darwin (which lacks a version number)
- Add t-darwin-libgccs1 to enable libgcc_s.1.dylib compatibility build

2. Added libgcc-darwin-fix-reexport.patch:
- Remove reexport of darwin-unwind.ver symbols in libgcc_s.1.dylib
- These symbols (___register_frame_info, etc.) don't exist in libgcc
  on modern macOS as they come from libSystem

The original build failed with:
  Undefined symbols for architecture arm64:
    "___deregister_frame_info", referenced from:
       -reexported_symbols_list command line option
    ...

This occurred because darwin-unwind.ver lists unwinder symbols that are
excluded from libgcc (via libgcc-libsystem.ver) on macOS 11+ where they
are provided by the system's libSystem.

pkgs/development/compilers/gcc/patches/15/libgcc-darwin-detection.patch

@@ -1,11 +1,12 @@
 --- a/libgcc/config.host
 +++ b/libgcc/config.host
-@@ -239,7 +239,7 @@ case ${host} in
+@@ -239,8 +239,8 @@ case ${host} in
      x86_64-*-darwin2[0-2]*)
        tmake_file="t-darwin-min-11 t-darwin-libgccs1 $tmake_file"
        ;;
 -    *-*-darwin2*)
+-      tmake_file="t-darwin-min-11 $tmake_file"
 +    *-*-darwin2* | *-*-darwin)
-       tmake_file="t-darwin-min-11 $tmake_file"
++      tmake_file="t-darwin-min-11 t-darwin-libgccs1 $tmake_file"
        ;;
      *-*-darwin1[89]*)

pkgs/development/compilers/gcc/patches/15/libgcc-darwin-fix-reexport.patch

@@ -0,0 +1,11 @@
+--- a/libgcc/config/t-slibgcc-darwin
++++ b/libgcc/config/t-slibgcc-darwin
+@@ -139,8 +139,7 @@ libgcc_s.1.dylib: all-multi libgcc_s.$(SHLIB_SOVERSION)$(SHLIB_EXT)
+ 	  $(CC) -arch $${arch} -nodefaultlibs -dynamiclib -nodefaultrpaths \
+ 	    -o libgcc_s.1$(SHLIB_EXT)_T_$${mlib} \
+ 	    -Wl,-reexport_library,libgcc_s.$(SHLIB_SOVERSION)$(SHLIB_EXT)_T_$${mlib} \
+ 	    -lSystem \
+-	    -Wl,-reexported_symbols_list,$(srcdir)/config/darwin-unwind.ver \
+ 	    -install_name $(SHLIB_RPATH)/libgcc_s.1.dylib \
+ 	    -compatibility_version 1 -current_version 1.1 ; \
+ 	done

pkgs/development/compilers/gcc/patches/default.nix

@@ -160,13 +160,14 @@ optionals noSysDirs (
 
 ## Darwin
 
-# Fixes detection of Darwin on x86_64-darwin. Otherwise, GCC uses a deployment target of 10.5, which crashes ld64.
+# Fixes detection of Darwin on x86_64-darwin and aarch64-darwin. Otherwise, GCC uses a deployment target of 10.5, which crashes ld64.
+++ optional (is14 && stdenv.hostPlatform.isDarwin) ../patches/14/libgcc-darwin-detection.patch
+++ optional (atLeast15 && stdenv.hostPlatform.isDarwin) ../patches/15/libgcc-darwin-detection.patch
+
+# Fix libgcc_s.1.dylib build on Darwin 11+ by not reexporting unwind symbols that don't exist
 ++ optional (
-  is14 && stdenv.hostPlatform.isDarwin && stdenv.hostPlatform.isx86_64
-) ../patches/14/libgcc-darwin-detection.patch
-++ optional (
-  atLeast15 && stdenv.hostPlatform.isDarwin && stdenv.hostPlatform.isx86_64
-) ../patches/15/libgcc-darwin-detection.patch
+  atLeast15 && stdenv.hostPlatform.isDarwin
+) ../patches/15/libgcc-darwin-fix-reexport.patch
 
 # Fix detection of bootstrap compiler Ada support (cctools as) on Nix Darwin
 ++ optional (stdenv.hostPlatform.isDarwin && langAda) ./ada-cctools-as-detection-configure.patch