Add PWD to environment variable whitelist for RBE builds.

Test: Build aosp with USE_RBE=1.

Change-Id: I4b51fbde330c6129654aa74f8a58dccf62cfa11d
diff --git a/core/rbe.mk b/core/rbe.mk
index fb39d51..231859b 100644
--- a/core/rbe.mk
+++ b/core/rbe.mk
@@ -21,7 +21,7 @@
   else
     rbe_dir := $(HOME)/rbe
   endif
-  RBE_WRAPPER := $(rbe_dir)/rewrapper --labels=type=compile,lang=cpp,compiler=clang
+  RBE_WRAPPER := $(rbe_dir)/rewrapper --labels=type=compile,lang=cpp,compiler=clang --env_var_whitelist=PWD
 
   # Append rewrapper to existing *_WRAPPER variables so it's possible to
   # use both ccache and rewrapper.