vkjson: Move redefinition of FALLTHROUGH_INTENDED

The macro FALLTHROUGH_INTENDED is defined in both
vulkan/vkjson/vkjson.h and android-base/macros.h, causing build errors
for any other modules that include both header files.

Move the redefinition to vkjson.cc.

Note that <android-base/macros.h> is not available for the libvkjson_ndk
build, so we cannot use that version of the macro and eliminate the
redefinition entirely.

Bug: 372694741
Test: CQ
Flag: EXEMPT bugfix
Change-Id: I02a0f2a50f3807ca932e84a5a002598b04c5f92a

Author: timvpGoogle

vulkan/vkjson/vkjson.cc

@@ -38,6 +38,12 @@
 
 namespace {
 
+/*
+ * Annotation to tell clang that we intend to fall through from one case to
+ * another in a switch. Sourced from android-base/macros.h.
+ */
+#define FALLTHROUGH_INTENDED [[clang::fallthrough]]
+
 inline bool IsIntegral(double value) {
 #if defined(ANDROID)
   // Android NDK doesn't provide std::trunc yet

vulkan/vkjson/vkjson.h

@@ -33,12 +33,6 @@
 #undef max
 #endif
 
-/*
- * Annotation to tell clang that we intend to fall through from one case to
- * another in a switch. Sourced from android-base/macros.h.
- */
-#define FALLTHROUGH_INTENDED [[clang::fallthrough]]
-
 struct VkJsonLayer {
   VkLayerProperties properties;
   std::vector<VkExtensionProperties> extensions;