Auto merge of #5123 - colby-swandale:fix-otool-ldd-check, r=segiddins

use Bundler.which to check for otool and ldd

Hi, there is some weird behaviour in `bundler doctor`. Bundler is checking for the existence of the `ldd` and `otool` commands but is not correctly redirecting the output of `otool`. Example being on the latest version of bundler:

```
› bundle doctor
llvm-otool(1): Apple Inc. version cctools-895
llvm-otool(1): Apple Inc. version cctools-895
llvm-otool(1): Apple Inc. version cctools-895
llvm-otool(1): Apple Inc. version cctools-895
llvm-otool(1): Apple Inc. version cctools-895
llvm-otool(1): Apple Inc. version cctools-895
```
 This is happening on Mac OS (10.12). I have refactored the check of these tool using the built in `command` function, this lets us check for the existence of these commands without actually having to execute them.

Thanks.

1 files changed, 2 insertions, 2 deletions

diff --git a/lib/bundler/cli/doctor.rb b/lib/bundler/cli/doctor.rb
index 728662024b..ae27983240 100644
--- a/lib/bundler/cli/doctor.rb
+++ b/lib/bundler/cli/doctor.rb
@@ -14,11 +14,11 @@ module Bundler
     end
 
     def otool_available?
-      system("otool --version 2>#{Bundler::NULL} >#{Bundler::NULL}")
+      Bundler.which("otool")
     end
 
     def ldd_available?
-      !system("ldd --help 2>#{Bundler::NULL} >#{Bundler::NULL}").nil?
+      Bundler.which("ldd")
     end
 
     def dylibs_darwin(path)