mk: introduce global-incdirs_ext-y

Introduce the global-incdirs_ext-y variable to deal with including
header files from outside of this git (optee_os.git).

Signed-off-by: Jens Wiklander <[email protected]>
Reviewed-by: Etienne Carriere <[email protected]>
Reviewed-by: Jerome Forissier <[email protected]>

mk/subdir.mk

@@ -111,8 +111,8 @@ endif
 
 include $1/sub.mk
 sub-subdirs := $$(addprefix $1/,$$(subdirs-y)) $$(subdirs_ext-y)
+incdirs$(sm) := $(incdirs$(sm)) $$(addprefix $1/,$$(global-incdirs-y)) $$(global-incdirs_ext-y)
 cppflags$(sm) := $$(cppflags$(sm)) $$(global-cppflags-y)
-incdirs$(sm) := $(incdirs$(sm)) $$(addprefix $1/,$$(global-incdirs-y))
 thissubdir-incdirs := $(out-dir)/$(base-prefix)$1 $$(addprefix $1/,$$(incdirs-y)) $$(incdirs_ext-y)
 ifneq ($$(libname),)
 incdirs-lib$$(libname)-$$(sm) := $$(incdirs-lib$$(libname)-$$(sm)) $$(addprefix $1/,$$(incdirs-lib-y))
@@ -140,6 +140,7 @@ aflags-remove-y :=
 subdirs-y :=
 subdirs_ext-y :=
 global-incdirs-y :=
+global-incdirs_ext-y :=
 global-cppflags-y :=
 incdirs-lib-y :=
 incdirs-y :=