Remove variables exported by Soong

LLVM_RELEASE_VERSION is unused from envsetup.sh and during product
config loading.  LLVM_PREBUILTS_VERSION is still used in envsetup.sh, so
needs to stay.

Delay reading core/clang/config.mk until after Soong's variables are
read so that we don't need a copy of LLVM_PREBUILTS_BASE.

Test: Compare build-aosp_flounder.ninja
Change-Id: I85b5836a2230838c8f3766fb19c6108fc5c9ca50

core/clang/config.mk

@@ -1,14 +1,7 @@
 ## Clang configurations.
 
-LLVM_PREBUILTS_PATH := $(LLVM_PREBUILTS_BASE)/$(BUILD_OS)-x86/$(LLVM_PREBUILTS_VERSION)/bin
 LLVM_RTLIB_PATH := $(LLVM_PREBUILTS_PATH)/../lib64/clang/$(LLVM_RELEASE_VERSION)/lib/linux/
 
-# These will come from Soong, drop the environment versions
-unexport CLANG
-unexport CLANG_CXX
-unexport CCC_CC
-unexport CCC_CXX
-
 CLANG_TBLGEN := $(BUILD_OUT_EXECUTABLES)/clang-tblgen$(BUILD_EXECUTABLE_SUFFIX)
 LLVM_TBLGEN := $(BUILD_OUT_EXECUTABLES)/llvm-tblgen$(BUILD_EXECUTABLE_SUFFIX)
 

core/clang/versions.mk

@@ -1,5 +1,3 @@
 ## Clang/LLVM release versions.
 
-LLVM_RELEASE_VERSION := 3.8
 LLVM_PREBUILTS_VERSION ?= clang-3289846
-LLVM_PREBUILTS_BASE ?= prebuilts/clang/host

core/config.mk

@@ -716,8 +716,11 @@ $(TARGET_2ND_ARCH_VAR_PREFIX)DEX2OAT_TARGET_CPU_VARIANT := $(call first_non_empt
 $(TARGET_2ND_ARCH_VAR_PREFIX)DEX2OAT_TARGET_INSTRUCTION_SET_FEATURES := default
 endif
 
-# define clang/llvm tools and global flags
-include $(BUILD_SYSTEM)/clang/config.mk
+# These will come from Soong, drop the environment versions
+unexport CLANG
+unexport CLANG_CXX
+unexport CCC_CC
+unexport CCC_CXX
 
 # ###############################################################
 # Collect a list of the SDK versions that we could compile against

core/main.mk

@@ -50,6 +50,8 @@ endif
 
 include $(SOONG_MAKEVARS_MK)
 
+include $(BUILD_SYSTEM)/clang/config.mk
+
 # Write the build number to a file so it can be read back in
 # without changing the command line every time.  Avoids rebuilds
 # when using ninja.