Switch to detecting clang rather than gcc

gcc makes it impossible to detect that it is gcc via --version
so instead detect clang and assume gcc if not clang.

Fixes #7218

glfw/glfw.py

@@ -46,7 +46,6 @@ class BinaryArch(NamedTuple):
     isa: ISA = ISA.AMD64
 
 
-
 class Env:
 
     cc: List[str] = []
@@ -89,8 +88,8 @@ class Env:
         return self._cc_version_string
 
     @property
-    def is_gcc(self) -> bool:
-        return 'gcc' in self.cc_version_string.split(maxsplit=1)[0].lower()
+    def is_clang(self) -> bool:
+        return 'clang' in self.cc_version_string.split(maxsplit=1)[0].lower()
 
     def copy(self) -> 'Env':
         ans = Env(self.cc, list(self.cppflags), list(self.cflags), list(self.ldflags), dict(self.library_paths), list(self.ldpaths), self.ccver)

setup.py

@@ -701,11 +701,11 @@ def get_source_specific_cflags(env: Env, src: str) -> List[str]:
             ans.append('-msse4.2' if '128' in src else '-mavx2')
             if '256' in src:
                 # We have manual vzeroupper so prevent compiler from emitting it causing duplicates
-                if env.is_gcc:
-                    ans.append('-mno-vzeroupper')
-                else:
+                if env.is_clang:
                     ans.append('-mllvm')
                     ans.append('-x86-use-vzeroupper=0')
+                else:
+                    ans.append('-mno-vzeroupper')
         elif env.binary_arch.isa != ISA.ARM64:
             ans.append('-DKITTY_NO_SIMD')
     elif src.startswith('3rdparty/base64/lib/arch/'):
@@ -1170,7 +1170,7 @@ def build_launcher(args: Options, launcher_dir: str = '.', bundle_type: str = 's
             sanitize_args = get_sanitize_args(env.cc, env.ccver)
             cflags.extend(sanitize_args)
             ldflags.extend(sanitize_args)
-            libs += ['-lasan'] if not is_macos and env.is_gcc else []
+            libs += ['-lasan'] if not is_macos and not env.is_clang else []
         else:
             cflags.append('-g')
         if args.profile: