In build_tc.py detect and avoid the duplicate toolchain building.

Test
./build_tc.py -b daisy,lumpy,stumpy -c ~/ssd/cros1/ -g ~/google46/
and watch the output, ensure there are only two buildings of gcc.

PRESUBMIT=passed
R=asharif,cmtice,shenhan,llozano,yunlian
CC=c-compiler-chrome
APPROVED=yunlian
DELTA=12  (5 added, 2 deleted, 5 changed)
OCL=65433-p2
RCL=65556-p2
RDATE=2013/01/30 17:21:57


P4 change: 42806508
1 file changed
tree: 6acd09e7d3a2927e707076bd7756dcfd2ef54560
  1. .git5_specs/
  2. v14/