Some small improvements to the build_tools

Summary: Closes https://github.com/facebook/rocksdb/pull/3664

Differential Revision: D7459433

Pulled By: sagar0

fbshipit-source-id: 3817e5d45fc70e83cb26f9800eaa0f4566c8dc0e

build_tools/build_detect_platform

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env bash
 #
 # Detects OS we're compiling on and outputs a file specified by the first
 # argument, which in turn gets read while processing Makefile.
@@ -66,11 +66,23 @@ rm -f "$OUTPUT"
 touch "$OUTPUT"
 
 if test -z "$CC"; then
+    if [ -x "$(command -v cc)" ]; then
         CC=cc
+    elif [ -x "$(command -v clang)" ]; then
+        CC=clang
+    else
+        CC=cc
+    fi
 fi
 
 if test -z "$CXX"; then
+    if [ -x "$(command -v g++)" ]; then
         CXX=g++
+    elif [ -x "$(command -v clang++)" ]; then
+        CXX=clang++
+    else
+        CXX=g++
+    fi
 fi
 
 # Detect OS
@@ -87,7 +99,7 @@ if test -z "$CLANG_SCAN_BUILD"; then
 fi
 
 if test -z "$CLANG_ANALYZER"; then
-    CLANG_ANALYZER=$(which clang++ 2> /dev/null)
+    CLANG_ANALYZER=$(command -v clang++ 2> /dev/null)
 fi
 
 if test -z "$FIND"; then
@@ -498,9 +510,9 @@ if test -z "$PORTABLE"; then
   elif test -n "`echo $TARGET_ARCHITECTURE | grep ^arm`"; then
     # TODO: Handle this with approprite options.
     COMMON_FLAGS="$COMMON_FLAGS"
-  elif [ "$TARGET_OS" == IOS ]; then
+  elif [ "$TARGET_OS" == "IOS" ]; then
     COMMON_FLAGS="$COMMON_FLAGS"
-  elif [ "$TARGET_OS" != AIX ] && [ "$TARGET_OS" != SunOS ]; then
+  elif [ "$TARGET_OS" != "AIX" ] && [ "$TARGET_OS" != "SunOS" ]; then
     COMMON_FLAGS="$COMMON_FLAGS -march=native "
   elif test "$USE_SSE"; then
     COMMON_FLAGS="$COMMON_FLAGS -msse4.2 -mpclmul"

build_tools/version.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env bash
 if [ "$#" = "0" ]; then
   echo "Usage: $0 major|minor|patch|full"
   exit 1