kbuild: properly pass options to hostcc when doing make O=..
This fix a longstanding bug where proper options was not
passed to hostcc in case of a make O=.. build.
This bug showed up in (not yet merged) klibc, and is not known
to have any counterpart in-kernel.
Fixed by moving the flags macro to Kbuild.include so it can be used
by both Makefile.lib and Makefile.host.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index 59620b1..b0d067b 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -87,6 +87,11 @@
# $(Q)$(MAKE) $(build)=dir
build := -f $(if $(KBUILD_SRC),$(srctree)/)scripts/Makefile.build obj
+# Prefix -I with $(srctree) if it is not an absolute path
+addtree = $(if $(filter-out -I/%,$(1)),$(patsubst -I%,-I$(srctree)/%,$(1))) $(1)
+# Find all -I options and call addtree
+flags = $(foreach o,$($(1)),$(if $(filter -I%,$(o)),$(call addtree,$(o)),$(o)))
+
# If quiet is set, only print short version of command
cmd = @$(echo-cmd) $(cmd_$(1))