[cmake] CheckIfuncSupport.cmake: Don't check for NOT DEFINED HAVE_IFUNC.

Otherwise, if I add -fsanitize in a later run, IFUNC will remain enabled,
resulting in SIGSEGV.

Also, add checks for CFLAGS/CXXFLAGS in specific build types, similar to
libromdata.

cmake/macros/CheckIfuncSupport.cmake

@@ -2,40 +2,40 @@
 # Requires ELF. Currently supported by gcc, but not clang.
 
 FUNCTION(CHECK_IFUNC_SUPPORT)
-	IF(NOT DEFINED HAVE_IFUNC)
-		# NOTE: ${CMAKE_MODULE_PATH} has two directories, macros/ and libs/,
-		# so we have to configure this manually.
-		SET(IFUNC_SOURCE_PATH "${CMAKE_SOURCE_DIR}/cmake/macros")
+	# NOTE: ${CMAKE_MODULE_PATH} has two directories, macros/ and libs/,
+	# so we have to configure this manually.
+	SET(IFUNC_SOURCE_PATH "${CMAKE_SOURCE_DIR}/cmake/macros")
 
-		# NOTE: If -fsanitize is specified, disable IFUNC.
-		# Otherwise, SIGSEGV will happen.
-		IF(CMAKE_C_FLAGS MATCHES -fsanitize OR CMAKE_CXX_FLAGS MATCHES -fsanitize)
-			SET(IS_SANITIZE 1)
-		ENDIF()
+	# NOTE: If -fsanitize is specified, disable IFUNC.
+	# Otherwise, SIGSEGV will happen.
+	IF(CMAKE_C_FLAGS MATCHES "-fsanitize" OR CMAKE_CXX_FLAGS MATCHES "-fsanitize")
+		SET(IS_SANITIZE 1)
+	ELSEIF(CMAKE_C_FLAGS_${BUILD_TYPE_UCASE} MATCHES "-fsanitize" OR CMAKE_CXX_FLAGS_${BUILD_TYPE_UCASE} MATCHES "-fsanitize")
+		SET(IS_SANITIZE 1)
+	ENDIF()
 
-		# Check for IFUNC support.
-		MESSAGE(STATUS "Checking if IFUNC is supported")
-		IF(WIN32 OR APPLE)
-			# No IFUNC for Windows or Mac OS X.
-			# Shortcut here to avoid needing a cross-compiled test program.
+	# Check for IFUNC support.
+	MESSAGE(STATUS "Checking if IFUNC is supported")
+	IF(WIN32 OR APPLE)
+		# No IFUNC for Windows or Mac OS X.
+		# Shortcut here to avoid needing a cross-compiled test program.
+		MESSAGE(STATUS "Checking if IFUNC is supported - no")
+		SET(TMP_HAVE_IFUNC FALSE)
+	ELSEIF(IS_SANITIZE)
+		MESSAGE(STATUS "Checking if IFUNC is supported - disabled due to -fsanitize")
+		SET(TMP_HAVE_IFUNC FALSE)
+	ELSE()
+		TRY_RUN(TMP_HAVE_IFUNC_RUN TMP_HAVE_IFUNC_COMPILE
+			"${CMAKE_BINARY_DIR}"
+			"${IFUNC_SOURCE_PATH}/IfuncTest.c")
+		IF(TMP_HAVE_IFUNC_COMPILE AND (TMP_HAVE_IFUNC_RUN EQUAL 0))
+			MESSAGE(STATUS "Checking if IFUNC is supported - yes")
+			SET(TMP_HAVE_IFUNC TRUE)
+		ELSE()
 			MESSAGE(STATUS "Checking if IFUNC is supported - no")
 			SET(TMP_HAVE_IFUNC FALSE)
-		ELSEIF(IS_SANITIZE)
-			MESSAGE(STATUS "Checking if IFUNC is supported - disabled due to -fsanitize")
-			SET(TMP_HAVE_IFUNC FALSE)
-		ELSE()
-			TRY_RUN(TMP_HAVE_IFUNC_RUN TMP_HAVE_IFUNC_COMPILE
-				"${CMAKE_BINARY_DIR}"
-				"${IFUNC_SOURCE_PATH}/IfuncTest.c")
-			IF(TMP_HAVE_IFUNC_COMPILE AND (TMP_HAVE_IFUNC_RUN EQUAL 0))
-				MESSAGE(STATUS "Checking if IFUNC is supported - yes")
-				SET(TMP_HAVE_IFUNC TRUE)
-			ELSE()
-				MESSAGE(STATUS "Checking if IFUNC is supported - no")
-				SET(TMP_HAVE_IFUNC FALSE)
-			ENDIF()
 		ENDIF()
-
-		SET(HAVE_IFUNC ${TMP_HAVE_IFUNC} CACHE INTERNAL "Is IFUNC supported?")
 	ENDIF()
+
+	SET(HAVE_IFUNC ${TMP_HAVE_IFUNC} CACHE INTERNAL "Is IFUNC supported?")
 ENDFUNCTION(CHECK_IFUNC_SUPPORT)