meson: clear flags used for build

Some were duplicated between GCC and Clange. Others were missing in
Clang case. Instead test all the flags and don't make assumptions that
will get invalid over time. Testing flags is almost free.

meson.build

@@ -266,41 +266,31 @@ cc = meson.get_compiler('c')
 flags = ['-D_FILE_OFFSET_BITS=64']
 link_flags = []
 
-test_flags = ['-Werror=implicit-function-declaration',
+test_flags = ['-Wdisabled-optimization',
-              '-Wno-missing-field-initializers',
-              '-Wno-sign-compare',
-              '-Wno-unused-parameter',
-              '-Wno-cast-function-type',
               '-Wempty-body',
-              '-Wdisabled-optimization',
+              '-Wformat',
-              '-Wstrict-prototypes',
-              '-Wno-format-zero-length',
-              '-Wno-redundant-decls',
-              '-Wvla',
-              '-Wno-format-truncation',
               '-Wimplicit-fallthrough',
+              '-Wmissing-prototypes',
+              '-Wparentheses',
+              '-Wpointer-arith',
+              '-Wshadow',
+              '-Wstrict-prototypes',
+              '-Wundef',
+              '-Wvla',
+              '-Werror=implicit-function-declaration',
+              '-Wno-cast-function-type',
+              '-Wno-format-zero-length',
+              '-Wno-missing-field-initializers',
+              '-Wno-pointer-sign',
+              '-Wno-sign-compare',
+              '-Wno-switch',
+              '-Wno-unused-parameter',
               '-fno-math-errno']
 
 flags += cc.get_supported_arguments(test_flags)
 
 if cc.has_multi_arguments('-Wformat', '-Werror=format-security')
-    flags += ['-Wformat', '-Werror=format-security']
+    flags += '-Werror=format-security'
-endif
-
-if cc.get_id() == 'gcc'
-    gcc_flags = ['-Wundef', '-Wmissing-prototypes', '-Wshadow',
-                 '-Wno-switch', '-Wparentheses', '-Wpointer-arith',
-                 '-Wno-pointer-sign',
-                 # GCC bug 66425
-                 '-Wno-unused-result']
-    flags += gcc_flags
-endif
-
-if cc.get_id() == 'clang'
-    clang_flags = ['-Wno-logical-op-parentheses', '-Wno-switch',
-                   '-Wno-tautological-compare', '-Wno-pointer-sign',
-                   '-Wno-tautological-constant-out-of-range-compare']
-    flags += clang_flags
 endif
 
 darwin = host_machine.system() == 'darwin'