Enforce C99 explicitly

CMakeLists.txt

@@ -564,6 +564,7 @@ add_library(capstone::capstone ALIAS capstone)
 target_include_directories(capstone PUBLIC
     $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
 )
+set_property(TARGET capstone PROPERTY C_STANDARD 99)
 
 if(BUILD_SHARED_LIBS)
     target_compile_definitions(capstone PUBLIC CAPSTONE_SHARED)

Makefile

@@ -45,6 +45,9 @@ else
 CFLAGS ?= -O3
 endif
 
+# C99 has been enforced elsewhere like xcode
+CFLAGS += -std=gnu99
+
 ifneq (,$(findstring yes,$(CAPSTONE_X86_ATT_DISABLE)))
 CFLAGS += -DCAPSTONE_X86_ATT_DISABLE
 endif