Prefer /usr/bin/env xxx over /usr/bin/xxx where xxx = perl, python, awk

Allow users to use a non-system version of perl, python and awk, which is useful
in certain package managers.

Reviewed By: JDevlieghere, MaskRay

Differential Revision: https://reviews.llvm.org/D95119

utils/GenLibDeps.pl

@@ -1,4 +1,4 @@
-#!/usr/bin/perl -w
+#!/usr/bin/env perl
 #
 # Program:  GenLibDeps.pl
 #

utils/codegen-diff

@@ -1,4 +1,4 @@
-#!/usr/bin/perl
+#!/usr/bin/env perl
 
 use Getopt::Std;
 $DEBUG = 0;

utils/findsym.pl

@@ -1,4 +1,4 @@
-#!/usr/bin/perl -w
+#!/usr/bin/env perl
 #
 # Program:  findsym.pl
 #
@@ -8,6 +8,8 @@
 # Syntax:   findsym.pl <directory_with_libraries_in_it> <symbol>
 #
 
+use warnings;
+
 # Give first option a name.
 my $Directory = $ARGV[0];
 my $Symbol = $ARGV[1];

utils/llvm-compilers-check

@@ -1,4 +1,4 @@
-#!/usr/bin/python3
+#!/usr/bin/env python3
 ##===- utils/llvmbuild - Build the LLVM project ----------------*-python-*-===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

utils/llvm-native-gxx

@@ -1,4 +1,4 @@
-#!/usr/bin/perl
+#!/usr/bin/env perl
 # Wrapper around LLVM tools to generate a native .o from llvm-gxx using an
 # LLVM back-end (CBE by default).