kbuild: introduce ld-option

ld-option is used to check if $(LD) supports a specific option.

Based on patch from Andi Kleen.

Cc: Andi Kleen <[email protected]>
Signed-off-by: Sam Ravnborg <[email protected]>
First use is to check if option -X is supported (upcoming patch).
Theis is ne

Documentation/kbuild/makefiles.txt

@@ -18,6 +18,7 @@ This document describes the Linux kernel Makefiles.
 	   --- 3.9 Dependency tracking
 	   --- 3.10 Special Rules
 	   --- 3.11 $(CC) support functions
+	   --- 3.12 $(LD) support functions
 
 	=== 4 Host Program support
 	   --- 4.1 Simple Host Program
@@ -570,6 +571,19 @@ more details, with real examples.
 			endif
 		endif
 
+--- 3.12 $(LD) support functions
+
+    ld-option
+	ld-option is used to check if $(LD) supports the supplied option.
+	ld-option takes two options as arguments.
+	The second argument is an optional option that can be used if the
+	first option is not supported by $(LD).
+
+	Example:
+		#Makefile
+		LDFLAGS_vmlinux += $(call really-ld-option, -X)
+
+
 === 4 Host Program support
 
 Kbuild supports building executables on the host for use during the

scripts/Kbuild.include

@@ -83,11 +83,12 @@ TMPOUT := $(if $(KBUILD_EXTMOD),$(firstword $(KBUILD_EXTMOD))/)
 # is automatically cleaned up.
 try-run = $(shell set -e;		\
 	TMP="$(TMPOUT).$$$$.tmp";	\
+	TMPO="$(TMPOUT).$$$$.o";	\
 	if ($(1)) >/dev/null 2>&1;	\
 	then echo "$(2)";		\
 	else echo "$(3)";		\
 	fi;				\
-	rm -f "$$TMP")
+	rm -f "$$TMP" "$$TMPO")
 
 # as-option
 # Usage: cflags-y += $(call as-option,-Wa$(comma)-isa=foo,)
@@ -135,6 +136,11 @@ cc-ifversion = $(shell [ $(call cc-version, $(CC)) $(1) $(2) ] && echo $(3))
 cc-ldoption = $(call try-run,\
 	$(CC) $(1) -nostdlib -xc /dev/null -o "$$TMP",$(1),$(2))
 
+# ld-option
+# Usage: LDFLAGS += $(call ld-option, -X)
+ld-option = $(call try-run,\
+	$(CC) /dev/null -c -o "$$TMPO" ; $(LD) $(1) "$$TMPO" -o "$$TMP",$(1),$(2))
+
 ######
 
 ###