make: add own file for CFLAGS feature tests

Makefile.cflags

@@ -0,0 +1,23 @@
+# Test if the input language was specified externally.
+# Otherwise test if the compiler unterstands the "-std=gnu99" flag, and use it if so.
+# Otherwise test if the compiler unterstands the "-std=c99" flag, and use it if so.
+ifeq ($(filter -std=%,$(CFLAGS)),)
+ifeq ($(shell $(CC) -std=gnu99 -E - 2>/dev/null >/dev/null </dev/null ; echo $$?),0)
+CFLAGS += -std=gnu99
+else
+ifeq ($(shell $(CC) -std=c99 -E - 2>/dev/null >/dev/null </dev/null ; echo $$?),0)
+CFLAGS += -std=c99
+endif
+endif
+endif
+
+# Add `-fno-delete-null-pointer-checks` flag iff the compiler supports it.
+# GCC removes moves tests whether `x == NULL`, if previously `x` or even `x->y` was accessed.
+# 0x0 might be a sane memory location for embedded systems, so the test must not be removed.
+# Right now clang does not use the *delete-null-pointer* optimization, and does not understand the parameter.
+# Related issues: #628, #664.
+ifeq ($(shell $(CC) -fno-delete-null-pointer-checks -E - 2>/dev/null >/dev/null </dev/null ; echo $$?),0)
+ifeq ($(shell LANG=C $(CC) -fno-delete-null-pointer-checks -E - 2>&1 1>/dev/null </dev/null | grep warning: | grep -- -fno-delete-null-pointer-checks),)
+CFLAGS += -fno-delete-null-pointer-checks
+endif
+endif

Makefile.include

@@ -54,29 +54,8 @@ ifneq (, $(filter $(DISABLE_MODULE), $(USEMODULE)))
 $(error "Required modules were disabled using DISABLE_MODULE: $(sort $(filter $(DISABLE_MODULE), $(USEMODULE)))")
 endif
 
-# Test if the input language was specified externally.
-# Otherwise test if the compiler unterstands the "-std=gnu99" flag, and use it if so.
-# Otherwise test if the compiler unterstands the "-std=c99" flag, and use it if so.
-ifeq ($(filter -std=%,$(CFLAGS)),)
-ifeq ($(shell $(CC) -std=gnu99 -E - 2>/dev/null >/dev/null </dev/null ; echo $$?),0)
-CFLAGS += -std=gnu99
-else
-ifeq ($(shell $(CC) -std=c99 -E - 2>/dev/null >/dev/null </dev/null ; echo $$?),0)
-CFLAGS += -std=c99
-endif
-endif
-endif
-
-# Add `-fno-delete-null-pointer-checks` flag iff the compiler supports it.
-# GCC removes moves tests whether `x == NULL`, if previously `x` or even `x->y` was accessed.
-# 0x0 might be a sane memory location for embedded systems, so the test must not be removed.
-# Right now clang does not use the *delete-null-pointer* optimization, and does not understand the parameter.
-# Related issues: #628, #664.
-ifeq ($(shell $(CC) -fno-delete-null-pointer-checks -E - 2>/dev/null >/dev/null </dev/null ; echo $$?),0)
-ifeq ($(shell LANG=C $(CC) -fno-delete-null-pointer-checks -E - 2>&1 1>/dev/null </dev/null | grep warning: | grep -- -fno-delete-null-pointer-checks),)
-CFLAGS += -fno-delete-null-pointer-checks
-endif
-endif
+# Feature test default CFLAGS and LINKFLAGS for the set compiled.
+include $(RIOTBASE)/Makefile.cflags
 
 # your binaries to link
 BASELIBS += $(BINDIR)$(BOARD)_base.a