kbuild: replace cc-name test with CONFIG_CC_IS_CLANG

Evaluating cc-name invokes the compiler every time even when you are
not compiling anything, like 'make help'. This is not efficient.

The compiler type has been already detected in the Kconfig stage.
Use CONFIG_CC_IS_CLANG, instead.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Acked-by: Paul Burton <paul.burton@mips.com> (MIPS)
Acked-by: Joel Stanley <joel@jms.id.au>
diff --git a/Makefile b/Makefile
index 9aa352b..8d6529c3 100644
--- a/Makefile
+++ b/Makefile
@@ -702,7 +702,7 @@
 
 KBUILD_CFLAGS += $(stackp-flags-y)
 
-ifeq ($(cc-name),clang)
+ifdef CONFIG_CC_IS_CLANG
 KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,)
 KBUILD_CFLAGS += $(call cc-disable-warning, format-invalid-specifier)
 KBUILD_CFLAGS += $(call cc-disable-warning, gnu)
diff --git a/arch/mips/Makefile b/arch/mips/Makefile
index 15a84cf..6841049 100644
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -128,7 +128,7 @@
 # clang's output will be based upon the build machine. So for clang we simply
 # unconditionally specify -EB or -EL as appropriate.
 #
-ifeq ($(cc-name),clang)
+ifdef CONFIG_CC_IS_CLANG
 cflags-$(CONFIG_CPU_BIG_ENDIAN)		+= -EB
 cflags-$(CONFIG_CPU_LITTLE_ENDIAN)	+= -EL
 else
diff --git a/arch/mips/vdso/Makefile b/arch/mips/vdso/Makefile
index 34605ca..58a0315 100644
--- a/arch/mips/vdso/Makefile
+++ b/arch/mips/vdso/Makefile
@@ -10,7 +10,7 @@
 	$(filter -march=%,$(KBUILD_CFLAGS)) \
 	-D__VDSO__
 
-ifeq ($(cc-name),clang)
+ifdef CONFIG_CC_IS_CLANG
 ccflags-vdso += $(filter --target=%,$(KBUILD_CFLAGS))
 endif
 
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 17be664..8a2ce14 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -96,7 +96,7 @@
 aflags-$(CONFIG_CPU_LITTLE_ENDIAN)	+= -mabi=elfv2
 endif
 
-ifneq ($(cc-name),clang)
+ifndef CONFIG_CC_IS_CLANG
   cflags-$(CONFIG_CPU_LITTLE_ENDIAN)	+= -mno-strict-align
 endif
 
@@ -175,7 +175,7 @@
 # Work around gcc code-gen bugs with -pg / -fno-omit-frame-pointer in gcc <= 4.8
 # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=44199
 # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52828
-ifneq ($(cc-name),clang)
+ifndef CONFIG_CC_IS_CLANG
 CC_FLAGS_FTRACE	+= $(call cc-ifversion, -lt, 0409, -mno-sched-epilog)
 endif
 endif
diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
index 24b2fb1..800a10f 100644
--- a/scripts/Makefile.extrawarn
+++ b/scripts/Makefile.extrawarn
@@ -64,7 +64,7 @@
 KBUILD_CFLAGS += $(warning)
 else
 
-ifeq ($(cc-name),clang)
+ifdef CONFIG_CC_IS_CLANG
 KBUILD_CFLAGS += $(call cc-disable-warning, initializer-overrides)
 KBUILD_CFLAGS += $(call cc-disable-warning, unused-value)
 KBUILD_CFLAGS += $(call cc-disable-warning, format)