Fix icu cross-compilation

We need to pass the location of the icu build root for the BUILD platform with
the --with-cross-build option when configuring icu for cross-compilation (to
the HOST platform). I.e. we always need to build it for the BUILD
platform. Surely this could be done in a more elegant way, but I got lost in
the mess, and just hacked it in the cross-toolset rule in Makefile.in.

Change-Id: Ia5e9d13d01067c6dded1fdc86c56f8f39aae6bc8

Makefile.in

@@ -292,7 +292,13 @@ build-nocheck : export SKIP_TESTS := YES
 build-nocheck : build
 
 cross-toolset: bootstrap fetch
+# We need to build icu for the build platform, as building icu for the host
+# platform requires tools built as part of icu that can run on the build
+# platform. see --with-cross-build in icu/ExternalProject_icu.mk
+	$(GNUMAKE) gb_Side=build icu
+#
 	cd cross_toolset && $(GNUMAKE) -j $(PARALLELISM) $(GMAKE_OPTIONS)
+#
 ifneq (,$(filter DESKTOP,$(BUILD_TYPE)))
 ifneq (WNT,$(OS))
 # We need to build nss for nsinstall... See NSINSTALL=... in nss/makefile.mk

icu/ExternalProject_icu.mk

@@ -37,7 +37,7 @@ $(call gb_ExternalProject_get_state_target,icu,build) :
 	$(if $(filter YES,$(MINGW_SHARED_GCCLIB)),-shared-libgcc)" \
 	./configure
 	$(if $(filter YES,$(CROSS_COMPILING)),--build=$(BUILD_PLATFORM) --host=$(HOST_PLATFORM) \
-	--with-cross-build=$(call gb_UnpackedTarball_get_dir,icu)/source) \
+		--with-cross-build=$(subst $(INPATH),$(INPATH_FOR_BUILD),$(call gb_UnpackedTarball_get_dir,icu))/source) \
 	--enable-layout --disable-static --enable-shared --disable-samples \
 	&& $(GNUMAKE) \
 	&& for lib in icudata icuin icuuc icule icutu; do \
@@ -76,7 +76,7 @@ $(call gb_ExternalProject_get_state_target,icu,build) :
 		$(if $(filter TRUE,$(DISABLE_DYNLOADING)),--enable-static --disable-shared,\
 		--disable-static --enable-shared $(if $(filter ANDROID,$(OS)),--with-library-suffix=lo)) \
 		$(if $(filter YES,$(CROSS_COMPILING)),--build=$(BUILD_PLATFORM) --host=$(HOST_PLATFORM)\
-		--with-cross-build=$(call gb_UnpackedTarball_get_dir,icu)/source)\
+			--with-cross-build=$(subst $(INPATH),$(INPATH_FOR_BUILD),$(call gb_UnpackedTarball_get_dir,icu))/source)\
 	&& $(GNUMAKE) \
 	&& touch $@