Optimizations to abi checking.

We now add export_static_lib_headers, export_generated_headers to the
filters while dumping the abi of a library using header-abi-dumper
(through -I<dir> additions to the invocation of header-abi-dumper and
header-abi-linker)

Also add support for zipped reference source based abi dumps.

Test: mm -j64 in hardware/interfaces/nfc/default/1.0 produces
android.hardware.nfc@1.0.so.lsdump with abi filtered out using generated
headers.

Test: Copied the linked abi dumps produced by mm -j64 in bionic/libc to
prebuilts/abi-dumps/ndk and gzipped them. Ran mm -j64 again in
bionic/libc and verified header-abi-diff getting invoked.

Bug: 32750600

Change-Id: I26210af908c87a6143e39fa25f50307acb68a387
diff --git a/cc/makevars.go b/cc/makevars.go
index 8bf034a..a1e97a5 100644
--- a/cc/makevars.go
+++ b/cc/makevars.go
@@ -42,6 +42,7 @@
 	ctx.Strict("RS_LLVM_PREBUILTS_VERSION", "${config.RSClangVersion}")
 	ctx.Strict("RS_LLVM_PREBUILTS_BASE", "${config.RSClangBase}")
 	ctx.Strict("RS_LLVM_PREBUILTS_PATH", "${config.RSLLVMPrebuiltsPath}")
+	ctx.Strict("RS_LLVM_INCLUDES", "${config.RSIncludePath}")
 	ctx.Strict("RS_CLANG", "${config.RSLLVMPrebuiltsPath}/clang")
 	ctx.Strict("RS_LLVM_AS", "${config.RSLLVMPrebuiltsPath}/llvm-as")
 	ctx.Strict("RS_LLVM_LINK", "${config.RSLLVMPrebuiltsPath}/llvm-link")