Mark export/unexport as deprecated

Make it so that `export`/`unexport` are deprecated during product
configuration, but obsolete during Android.mk parsing (and later in the
build, since we can't un-obsolete it).

Remove some ccache / goma exports, those don't need to be exports, since
soong_ui asks about them explicitly. They also only run doing the
initial project configuration, so we don't run anything with that
environment.

Bug: 73959648
Test: m nothing
Test: build_test on all downstream branches
Change-Id: I55a749f46775660439ae57e881a02c914e83de16
diff --git a/core/ccache.mk b/core/ccache.mk
index 893c985..d10aceb 100644
--- a/core/ccache.mk
+++ b/core/ccache.mk
@@ -32,24 +32,24 @@
 ifneq ($(filter-out false,$(USE_CCACHE)),)
   # The default check uses size and modification time, causing false misses
   # since the mtime depends when the repo was checked out
-  export CCACHE_COMPILERCHECK ?= content
+  CCACHE_COMPILERCHECK ?= content
 
   # See man page, optimizations to get more cache hits
   # implies that __DATE__ and __TIME__ are not critical for functionality.
   # Ignore include file modification time since it will depend on when
   # the repo was checked out
-  export CCACHE_SLOPPINESS := time_macros,include_file_mtime,file_macro
+  CCACHE_SLOPPINESS := time_macros,include_file_mtime,file_macro
 
   # Turn all preprocessor absolute paths into relative paths.
   # Fixes absolute paths in preprocessed source due to use of -g.
   # We don't really use system headers much so the rootdir is
   # fine; ensures these paths are relative for all Android trees
   # on a workstation.
-  export CCACHE_BASEDIR := /
+  CCACHE_BASEDIR := /
 
   # Workaround for ccache with clang.
   # See http://petereisentraut.blogspot.com/2011/09/ccache-and-clang-part-2.html
-  export CCACHE_CPP2 := true
+  CCACHE_CPP2 := true
 
   ifndef CC_WRAPPER
     CC_WRAPPER := $(CCACHE_EXEC)