Plugin: Fix MacOS Build and test errors

- Build scripts now to g++13 with classic linker
- Catch2 picked fix catchorg/Catch2#2837

With the new macOS linker the build fails with a weird error.
Turned out, we need gcc13 together with the classic linker to successfully build on the github runner.

.github/workflows/make-release.yml

@@ -33,7 +33,7 @@ jobs:
 
     - name: Build and run CATCH2 tests
       run: |
-        make -C client/mumble-plugin/ CC=g++-11 test
+        make -C client/mumble-plugin/ CC=g++-13 CFLAGS+=-ld_classic test
 
     - name: Build Plugin
       run: |
@@ -126,7 +126,7 @@ jobs:
 
     - name: Build and run CATCH2 tests
       run: |
-        make -C client/mumble-plugin/ DEBUG+="-g3 -Og -DDEBUG" CC=g++-11 test
+        make -C client/mumble-plugin/ DEBUG+="-g3 -Og -DDEBUG" CC=g++-13 CFLAGS+=-ld_classic test
 
     - name: Build Plugin
       run: |

client/mumble-plugin/Makefile

@@ -151,10 +151,10 @@ plugin-win-dllresource:
 	$(mingwprefix)windres dllResource.rc dllResource.o
 
 # shortcut for building natively on macOS
-plugin-macOS: CC=g++-11
+plugin-macOS: CC=g++-13
 plugin-macOS: outname=fgcom-mumble-macOS.bundle
 plugin-macOS: openssl-macOS
-	make CC=$(CC) outname=$(outname) plugin
+	make CC=$(CC) outname=$(outname) CFLAGS+=-ld_classic plugin
 
 # OpenSSL
 # The sources are located under lib/openssl as git submodule, and supposed to point to the latest stable head

client/mumble-plugin/test/catch2/catch_amalgamated.hpp

@@ -87,6 +87,9 @@
 // See e.g.:
 // https://opensource.apple.com/source/CarbonHeaders/CarbonHeaders-18.1/TargetConditionals.h.auto.html
 #ifdef __APPLE__
+#  ifndef __has_extension
+#    define __has_extension(x) 0
+#  endif
 #  include <TargetConditionals.h>
 #  if (defined(TARGET_OS_OSX) && TARGET_OS_OSX == 1) || \
       (defined(TARGET_OS_MAC) && TARGET_OS_MAC == 1)