Cross-platform fix version.sh

version.sh now works also on linux properly.

build_tools/version.sh

@@ -1,14 +1,14 @@
 #!/bin/sh
-if [ $# == 0 ]; then
+if [ "$#" = "0" ]; then
   echo "Usage: $0 major|minor|patch"
   exit 1
 fi
-if [ $1 = "major" ]; then
+if [ "$1" = "major" ]; then
   cat include/rocksdb/version.h  | grep MAJOR | head -n1 | awk '{print $3}'
 fi
-if [ $1 = "minor" ]; then
+if [ "$1" = "minor" ]; then
   cat include/rocksdb/version.h  | grep MINOR | head -n1 | awk '{print $3}'
 fi
-if [ $1 = "patch" ]; then
+if [ "$1" = "patch" ]; then
   cat include/rocksdb/version.h  | grep PATCH | head -n1 | awk '{print $3}'
 fi