Bug 1288390 - avoid a few more warnings in third-party code when compiling with clang; r=mshal

extensions/spellcheck/hunspell/src/moz.build

@@ -32,3 +32,7 @@ ALLOW_COMPILER_WARNINGS = True
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
+if CONFIG['CLANG_CXX'] or CONFIG['CLANG_CL']:
+    CXXFLAGS += [
+        '-Wno-implicit-fallthrough',
+    ]

media/libstagefright/moz.build

@@ -169,4 +169,5 @@ elif CONFIG['GNU_CXX']:
             '-Wno-mismatched-tags',
             '-Wno-tautological-constant-out-of-range-compare',
             '-Wno-unreachable-code-return',
+            '-Wno-implicit-fallthrough',
         ]

media/libvpx/moz.build

@@ -98,6 +98,11 @@ if CONFIG['GNU_CC'] or CONFIG['CLANG_CL']:
         '-Wno-sign-compare',
         '-Wno-unused-function', # so many of these warnings; just ignore them
     ]
+if CONFIG['CLANG_CXX'] or CONFIG['CLANG_CL']:
+    CFLAGS += [
+        '-Wno-unreachable-code',
+        '-Wno-unneeded-internal-declaration',
+    ]
 
 ASFLAGS += CONFIG['VPX_ASFLAGS']
 ASFLAGS += [