Fix clang_analyze path in fbcode_config.sh

Summary: current clang_analyze path is broken, update it

Test Plan:
USE_CLANG=1 TEST_TMPDIR=/dev/shm/rocksdb OPT=-g make J=64 analyze -j64
make sure it works

Reviewers: yiwu, sdong, andrewkr

Reviewed By: andrewkr

Subscribers: andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D59505

build_tools/fbcode_config.sh

@@ -87,7 +87,7 @@ CLANG_LIB="$CLANG_BASE/lib"
 CLANG_SRC="$CLANG_BASE/../../src"
 
 CLANG_ANALYZER="$CLANG_BIN/clang++"
-CLANG_SCAN_BUILD="$CLANG_SRC/clang/tools/scan-build/scan-build"
+CLANG_SCAN_BUILD="$CLANG_SRC/llvm/tools/clang/tools/scan-build/bin/scan-build"
 
 if [ -z "$USE_CLANG" ]; then
   # gcc