kernel.mk: fix bison unable to find m4 file issue

Android builds a version of bison which is unusable outside the tree.
Since the bison is invoked in the KBUILD_OUTPUT dir, the error is
generated:

bison: external/bison/data/m4sugar/m4sugar.m4: cannot open: No such file or directory

To workaround it, add a symlink to the external dir so that bison can
get the expected m4 file.

diff --git a/build/tasks/kernel.mk b/build/tasks/kernel.mk
index cb9b22d..da84163 100644 (file)
--- a/build/tasks/kernel.mk
+++ b/build/tasks/kernel.mk
@@ -45,6 +45,7 @@ KERNEL_DOTCONFIG_FILE := $(KBUILD_OUTPUT)/.config
 KERNEL_ARCH_CHANGED := $(if $(filter 0,$(shell grep -s ^$(if $(filter x86,$(TARGET_KERNEL_ARCH)),\#.)CONFIG_64BIT $(KERNEL_DOTCONFIG_FILE) | wc -l)),FORCE)
 $(KERNEL_DOTCONFIG_FILE): $(KERNEL_CONFIG_FILE) $(wildcard $(TARGET_KERNEL_DIFFCONFIG)) $(KERNEL_ARCH_CHANGED)
        $(hide) mkdir -p $(@D) && cat $(wildcard $^) > $@
+       $(hide) ln -sf ../../../../../../external $(@D)
        $(mk_kernel) oldnoconfig
 
 # bison is needed to build kernel and external modules from source