Fix TARGET_PATH for external toolchain builds

TARGET_PATH didn't contain $(STAGING_DIR)/usr/bin, which means that
programs installed in $(STAGING_DIR)/usr/bin were not considered for
execution during Buildroot build process. This was a problem with host
automake/autoconf/libtool, which could not be found.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/Makefile.in

@@ -126,7 +126,7 @@ TOOLCHAIN_EXTERNAL_PATH:=$(strip $(subst ",, $(BR2_TOOLCHAIN_EXTERNAL_PATH)))
 #"))
 #TOOL_BUILD_DIR=$(BASE_DIR)/$(TOPDIR_PREFIX)toolchain_build_$(TOOLCHAIN_EXTERNAL_PREFIX)
 TOOL_BUILD_DIR=$(BASE_DIR)/$(TOPDIR_PREFIX)toolchain_build_$(ARCH)$(COND_ARCH_FPU_SUFFIX)$(TOPDIR_SUFFIX)
-TARGET_PATH="$(STAGING_DIR)/bin:$(TOOL_BUILD_DIR)/bin:$(TOOLCHAIN_EXTERNAL_PATH)/bin:$(PATH)"
+TARGET_PATH="$(STAGING_DIR)/bin:$(STAGING_DIR)/usr/bin:$(TOOL_BUILD_DIR)/bin:$(TOOLCHAIN_EXTERNAL_PATH)/bin:$(PATH)"
 #IMAGE:=$(BINARIES_DIR)/$(BR2_ROOTFS_PREFIX).$(TOOLCHAIN_EXTERNAL_PREFIX)$(ROOTFS_SUFFIX)
 IMAGE:=$(BINARIES_DIR)/$(BR2_ROOTFS_PREFIX).$(ARCH)$(COND_ARCH_FPU_SUFFIX)$(ROOTFS_SUFFIX)