build_tools/build_detect_version rocksdb_build_git_sha

[cxz19871115]

18 env -i git rev-parse HEAD 2>&1 |
19 awk '
20 BEGIN {
21 print "#include "build_version.h"\n"
22 }
23 { print "const char* rocksdb_build_git_sha = "rocksdb_build_git_sha:" $0"";" }
24 ' > ${VFILE}

in my pc, exec "env -i git rev-parse HEAD" failed, print two lines info, like this.
$ env -i git rev-parse HEAD
fatal: Not a git repository (or any parent up to mount parent /mnt)
Stopping at filesystem boundary (GIT_DISCOVERY_ACROSS_FILESYSTEM not set).

It can print two 'const char* rocksdb_build_git_sha = "rocksdb_build_git_sha:XXX" ' into util/build_version.cc, so that redifinition error happened when compiled src.

I think it is a bug, must to check result of command "env -i git rev-parse HEAD", to make sure the resutl just only one line.