build: change LDFLAGS/CFLAGS ordering.

Always use CFLAGS/LDFLAGS that point to headers and libvpx.a inside our
build tree before ones from the environment, which could reference
headers or libs outside the build tree.

This fixes issue 307.

Change-Id: I34d176b8c21098f6da5ea71f0147d3c49283cc45

build/make/Makefile

@@ -98,11 +98,11 @@ install::
 $(BUILD_PFX)%.c.d: %.c
 	$(if $(quiet),@echo "    [DEP] $@")
 	$(qexec)mkdir -p $(dir $@)
-	$(qexec)$(CC) $(CFLAGS) -M $< | $(fmt_deps) > $@
+	$(qexec)$(CC) $(INTERNAL_CFLAGS) $(CFLAGS) -M $< | $(fmt_deps) > $@
 
 $(BUILD_PFX)%.c.o: %.c
 	$(if $(quiet),@echo "    [CC] $@")
-	$(qexec)$(CC) $(CFLAGS) -c -o $@ $<
+	$(qexec)$(CC) $(INTERNAL_CFLAGS) $(CFLAGS) -c -o $@ $<
 
 $(BUILD_PFX)%.asm.d: %.asm
 	$(if $(quiet),@echo "    [DEP] $@")
@@ -188,7 +188,7 @@ define linker_template
 $(1): $(filter-out -%,$(2))
 $(1):
 	$(if $(quiet),@echo    "    [LD] $$@")
-	$(qexec)$$(LD) $$(strip $$(LDFLAGS) -o $$@ $(2) $(3) $$(extralibs))
+	$(qexec)$$(LD) $$(strip $$(INTERNAL_LDFLAGS) $$(LDFLAGS) -o $$@ $(2) $(3) $$(extralibs))
 endef
 # make-3.80 has a bug with expanding large input strings to the eval function,
 # which was triggered in some cases by the following component of

examples.mk

@@ -122,8 +122,8 @@ else
     LIB_PATH := $(call enabled,LIB_PATH)
     INC_PATH := $(call enabled,INC_PATH)
 endif
-CFLAGS += $(addprefix -I,$(INC_PATH))
-LDFLAGS += $(addprefix -L,$(LIB_PATH))
+INTERNAL_CFLAGS = $(addprefix -I,$(INC_PATH))
+INTERNAL_LDFLAGS += $(addprefix -L,$(LIB_PATH))
 
 
 # Expand list of selected examples to build (as specified above)
@@ -214,7 +214,8 @@ $(1): $($(1:.vcproj=).SRCS)
             --ver=$$(CONFIG_VS_VERSION)\
             --proj-guid=$$($$(@:.vcproj=).GUID)\
             $$(if $$(CONFIG_STATIC_MSVCRT),--static-crt) \
-            --out=$$@ $$(CFLAGS) $$(LDFLAGS) -l$$(CODEC_LIB) -lwinmm $$^
+            --out=$$@ $$(INTERNAL_CFLAGS) $$(CFLAGS) \
+            $$(INTERNAL_LDFLAGS) $$(LDFLAGS) -l$$(CODEC_LIB) -lwinmm $$^
 endef
 PROJECTS-$(CONFIG_MSVS) += $(ALL_EXAMPLES:.c=.vcproj)
 INSTALL-BINS-$(CONFIG_MSVS) += $(foreach p,$(VS_PLATFORMS),\