Remove MACOSX_DEPLOYMENT_TARGET (#1880)

It seems that this is no longer necessary for recent macOS .

CONTRIBUTING.md

@@ -63,7 +63,7 @@ cd audio
 git submodule update --init --recursive
 python setup.py develop
 # or, for OSX
-# MACOSX_DEPLOYMENT_TARGET=10.9 CC=clang CXX=clang++ python setup.py develop
+# CC=clang CXX=clang++ python setup.py develop
 ```
 
 Some environmnet variables that change the build behavior

README.md

@@ -64,7 +64,7 @@ The build process also builds the RNN transducer loss. This functionality can be
 python setup.py install
 
 # OSX
-MACOSX_DEPLOYMENT_TARGET=10.9 CC=clang CXX=clang++ python setup.py install
+CC=clang CXX=clang++ python setup.py install
 
 # Windows
 # We need to use the MSVC x64 toolset for compilation, with Visual Studio's vcvarsall.bat or directly with vcvars64.bat.

packaging/pkg_helpers.bash

@@ -141,7 +141,7 @@ setup_build_version() {
 # Set some useful variables for OS X, if applicable
 setup_macos() {
   if [[ "$(uname)" == Darwin ]]; then
-    export MACOSX_DEPLOYMENT_TARGET=10.9 CC=clang CXX=clang++
+    export CC=clang CXX=clang++
   fi
 }