tools/Makefile: Fix mistakes in earlier change, r4328
tools/Makefile: Fix mistakes in earlier change, r4328

These caused the toolchain build to fail on Linux.

Make sure we include tools/REVISIONS to get the new Git commit IDs.
(I thought "git checkout ''" would fail and so catch this mistake, but
actually this command seems to be a no-op in this case.)

Correct case: "src" -> "SRC".  (I tested on a Mac with a
case-insensitive filesystem which did not catch this mistake.)

BUG=http://code.google.com/p/nativeclient/issues/detail?id=1132
TEST="cd tools && make SDKLOC=`pwd`/sdk-dest" on Linux

Review URL: http://codereview.chromium.org/6531010

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@4331 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

sbc100/native_client,sbc100/native_client,nacl-webkit/native_client,nacl-webkit/native_client,sbc100/native_client,sbc100/native_client,nacl-webkit/native_client,sbc100/native_client,nacl-webkit/native_client,sbc100/native_client,nacl-webkit/native_client