[Analyzer] Use CC environment variable to select analyzer path in SATestBuild.

This change is required to easily test the given checkout of the analyzer,
rather than the one bundled with a system compiler.

Differential Revision: https://reviews.llvm.org/D38155

llvm-svn: 313927
diff --git a/clang/utils/analyzer/SATestBuild.py b/clang/utils/analyzer/SATestBuild.py
index 18c5393..2669b88 100755
--- a/clang/utils/analyzer/SATestBuild.py
+++ b/clang/utils/analyzer/SATestBuild.py
@@ -142,7 +142,10 @@
 #------------------------------------------------------------------------------
 
 # Find Clang for static analysis.
-Clang = which("clang", os.environ['PATH'])
+if 'CC' in os.environ:
+    Clang = os.environ['CC']
+else:
+    Clang = which("clang", os.environ['PATH'])
 if not Clang:
     print "Error: cannot find 'clang' in PATH"
     sys.exit(-1)