Use custom `MACOSX_DEPLOYMENT_TARGET` if defined (fixes #312)

plugins/python-build/bin/python-build

@@ -1815,10 +1815,12 @@ fi
 
 # Set MACOSX_DEPLOYMENT_TARGET from the product version of OS X (#219, #220)
 if [[ "Darwin" == "$(uname -s)" ]]; then
-  MACOS_VERSION="$(sw_vers -productVersion 2>/dev/null || true)"
-  MACOS_VERSION_ARRAY=(${MACOS_VERSION//\./ })
-  if [ "${#MACOS_VERSION_ARRAY[@]}" -ge 2 ]; then
-    export MACOSX_DEPLOYMENT_TARGET="${MACOS_VERSION_ARRAY[0]}.${MACOS_VERSION_ARRAY[1]}"
+  if [ -z "${MACOSX_DEPLOYMENT_TARGET}" ]; then
+    MACOS_VERSION="$(sw_vers -productVersion 2>/dev/null || true)"
+    MACOS_VERSION_ARRAY=(${MACOS_VERSION//\./ })
+    if [ "${#MACOS_VERSION_ARRAY[@]}" -ge 2 ]; then
+      export MACOSX_DEPLOYMENT_TARGET="${MACOS_VERSION_ARRAY[0]}.${MACOS_VERSION_ARRAY[1]}"
+    fi
   fi
 fi
 

plugins/python-build/test/pyenv_ext.bats

@@ -259,3 +259,24 @@ OUT
 PYTHON_CONFIGURE_OPTS_ARRAY=(--enable-universalsdk=/ --with-universal-archs=intel)
 EOS
 }
+
+@test "default MACOSX_DEPLOYMENT_TARGET" {
+  stub uname '-s : echo Darwin'
+  stub sw_vers '-productVersion : echo 10.10'
+
+  TMPDIR="$TMP" run_inline_definition <<OUT
+echo "\${MACOSX_DEPLOYMENT_TARGET}"
+OUT
+  assert_success
+  assert_output "10.10"
+}
+
+@test "use custom MACOSX_DEPLOYMENT_TARGET if defined" {
+  stub uname '-s : echo Darwin'
+
+  MACOSX_DEPLOYMENT_TARGET="10.4" TMPDIR="$TMP" run_inline_definition <<OUT
+echo "\${MACOSX_DEPLOYMENT_TARGET}"
+OUT
+  assert_success
+  assert_output "10.4"
+}