rocksdb: Update path to dev clang in fbcode

Summary: Current clang path in fbcode points to clang 3.5. This diff updates clang path to clang 3.7.

Test Plan:
Make sure clang 3.7 is in use and all tests are passing.
```lang=bash
% USE_CLANG make check
```

Reviewers: meyering, sdong, rven, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D34119

build_tools/fbcode_config.sh

@@ -92,8 +92,9 @@ DEPS_INCLUDE="$SNAPPY_INCLUDE $ZLIB_INCLUDE $BZIP_INCLUDE $LZ4_INCLUDE $GFLAGS_I
 GCC_BASE="/mnt/gvfs/third-party2/gcc/1c67a0b88f64d4d9ced0382d141c76aaa7d62fba/4.9.x/centos6-native/1317bc4"
 STDLIBS="-L $GCC_BASE/lib64"
 
-CLANG_BASE="/mnt/gvfs/third-party2/clang/290704c112bf894bf4a30d7bbd1be81e34998473/dev"
-CLANG_ANALYZER="$CLANG_BASE/centos6-native/af4b1a0/bin/clang++"
+CLANG_BASE="/mnt/gvfs/third-party2/clang/ab6260de0ba0af5cb84eb2df1844e277c7d68fbd/dev"
+CLANG_BIN="$CLANG_BASE/centos6-native/165e05b/bin"
+CLANG_ANALYZER="$CLANG_BIN/clang++"
 CLANG_SCAN_BUILD="$CLANG_BASE/src/clang/tools/scan-build/scan-build"
 
 if [ -z "$USE_CLANG" ]; then
@@ -106,9 +107,9 @@ if [ -z "$USE_CLANG" ]; then
   CFLAGS+=" -isystem $LIBGCC_INCLUDE"
 else
   # clang 
-  CLANG_INCLUDE="$CLANG_BASE/gcc-4.9-glibc-2.20/74c386f/lib/clang/dev/include/"
-  CC="$CLANG_BASE/centos6-native/af4b1a0/bin/clang"
-  CXX="$CLANG_BASE/centos6-native/af4b1a0/bin/clang++"
+  CLANG_INCLUDE="$CLANG_BASE/gcc-4.9-glibc-2.20/3ea62b1/lib/clang/dev/include/"
+  CC="$CLANG_BIN/clang"
+  CXX="$CLANG_BIN/clang++"
 
   KERNEL_HEADERS_INCLUDE="/mnt/gvfs/third-party2/kernel-headers/ffd14f660a43c4b92717986b1bba66722ef089d0/3.2.18_70_fbk11_00129_gc8882d0/gcc-4.9-glibc-2.20/da39a3e/include"