build system: make compiler names configurable

The top-level Makefile hardcoded the host and cross compiler name
to "gcc".  Make it possible to set different values either on the
command line (make CROSS_COMPILER=clang) or in the configuration
file.

1 files changed, 24 insertions, 2 deletions

diff --git a/Makefile b/Makefile
index f1d6b20b4..51f460583 100644
--- a/Makefile
+++ b/Makefile
@@ -196,6 +196,28 @@ ARCH ?= $(SUBARCH)
 # Architecture as present in compile.h
 UTS_MACHINE := $(ARCH)
 
+HOST_COMPILER ?=
+ifeq ($(HOST_COMPILER),)
+HOST_COMPILER := $(shell grep ^CONFIG_HOST_COMPILER= .config 2>/dev/null)
+HOST_COMPILER := $(subst CONFIG_HOST_COMPILER=,,$(HOST_COMPILER))
+HOST_COMPILER := $(subst ",,$(HOST_COMPILER))
+#")
+endif
+ifeq ($(HOST_COMPILER),)
+HOST_COMPILER := gcc
+endif
+
+CROSS_COMPILER ?=
+ifeq ($(CROSS_COMPILER),)
+CROSS_COMPILER := $(shell grep ^CONFIG_CROSS_COMPILER= .config 2>/dev/null)
+CROSS_COMPILER := $(subst CONFIG_CROSS_COMPILER=,,$(CROSS_COMPILER))
+CROSS_COMPILER := $(subst ",,$(CROSS_COMPILER))
+#")
+endif
+ifeq ($(CROSS_COMPILER),)
+CROSS_COMPILER := gcc
+endif
+
 # SHELL used by kbuild
 CONFIG_SHELL := $(shell if [ -x "$$BASH" ]; then echo $$BASH; \
           else if [ -x /bin/bash ]; then echo /bin/bash; \
@@ -275,7 +297,7 @@ export quiet Q KBUILD_VERBOSE
 # Look for make include files relative to root of kernel src
 MAKEFLAGS += --include-dir=$(srctree)
 
-HOSTCC          = gcc
+HOSTCC          = $(HOST_COMPILER)
 HOSTCXX         = g++
 HOSTCFLAGS      :=
 HOSTCXXFLAGS    :=
@@ -293,7 +315,7 @@ MAKEFLAGS += -rR
 # Make variables (CC, etc...)
 
 AS              = $(CROSS_COMPILE)as
-CC              = $(CROSS_COMPILE)gcc
+CC              = $(CROSS_COMPILE)$(CROSS_COMPILER)
 LD              = $(CC) -nostdlib
 CPP             = $(CC) -E
 AR              = $(CROSS_COMPILE)ar