configure: find MacOSX SDKs in /Applications/Xcode.app/Contents/Developer

... and also export DEVELOPER_DIR so that xcrun returns CC and CXX
values that match each other and the found SDK too, which was not
previously the case on oddly set up machines with multiple SDKs.

Change-Id: Iaed362b369b558b706926f1d15d170db580a4724

configure.ac

@@ -2539,6 +2539,14 @@ if test $_os = Darwin; then
             with_macosx_sdk=10.6
         elif test -d /Developer/SDKs/MacOSX10.7.sdk; then
             with_macosx_sdk=10.7
+        elif test -d "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.6.sdk"; then
+            with_macosx_sdk=10.6
+        elif test -d "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.7.sdk"; then
+            with_macosx_sdk=10.7
+        elif test -d "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk"; then
+            with_macosx_sdk=10.8
+        elif test -d "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk"; then
+            with_macosx_sdk=10.9
         elif test -x /usr/bin/xcode-select; then
             xcodepath="`xcode-select -print-path`"
             if test -d "$xcodepath/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.6.sdk"; then
@@ -2587,6 +2595,8 @@ if test $_os = Darwin; then
                 MACOSX_SDK_PATH=/Developer-old/SDKs/MacOSX10.6.sdk
             elif test -d /Xcode3/SDKs/MacOSX10.6.sdk; then
                 MACOSX_SDK_PATH=/Xcode3/SDKs/MacOSX10.6.sdk
+            elif test -d "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/$with_macosx_sdk.sdk"; then
+                MACOSX_SDK_PATH=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/$with_macosx_sdk.sdk
             elif test -x /usr/bin/xcode-select; then
                 xcodepath="`xcode-select -print-path`"
                 if test -d "$xcodepath/Platforms/MacOSX.platform/Developer/SDKs/MacOSX$with_macosx_sdk.sdk"; then
@@ -2597,6 +2607,8 @@ if test $_os = Darwin; then
         10.7)
             if test -d /Developer/SDKs/MacOSX$with_macosx_sdk.sdk; then
                 MACOSX_SDK_PATH=/Developer/SDKs/MacOSX$with_macosx_sdk.sdk
+            elif test -d "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/$with_macosx_sdk.sdk"; then
+                MACOSX_SDK_PATH=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/$with_macosx_sdk.sdk
             elif test -x /usr/bin/xcode-select; then
                 xcodepath="`xcode-select -print-path`"
                 if test -d "$xcodepath/Platforms/MacOSX.platform/Developer/SDKs/MacOSX$with_macosx_sdk.sdk"; then
@@ -2605,9 +2617,13 @@ if test $_os = Darwin; then
             fi
             ;;
         10.8|10.9)
-            xcodepath="`xcode-select -print-path`"
-            if test -d "$xcodepath/Platforms/MacOSX.platform/Developer/SDKs/MacOSX$with_macosx_sdk.sdk"; then
-                MACOSX_SDK_PATH="$xcodepath/Platforms/MacOSX.platform/Developer/SDKs/MacOSX$with_macosx_sdk.sdk"
+            if test -d "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/$with_macosx_sdk.sdk"; then
+                MACOSX_SDK_PATH=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/$with_macosx_sdk.sdk
+            else
+                xcodepath="`xcode-select -print-path`"
+                if test -d "$xcodepath/Platforms/MacOSX.platform/Developer/SDKs/MacOSX$with_macosx_sdk.sdk"; then
+                    MACOSX_SDK_PATH="$xcodepath/Platforms/MacOSX.platform/Developer/SDKs/MacOSX$with_macosx_sdk.sdk"
+                fi
             fi
             ;;
         esac
@@ -2625,6 +2641,10 @@ if test $_os = Darwin; then
         with_macosx_version_max_allowed="$with_macosx_sdk"
     fi
 
+    # export this so that "xcrun" invocations later return matching values
+    DEVELOPER_DIR="${MACOSX_SDK_PATH%/SDKs*}"
+    DEVELOPER_DIR="${DEVELOPER_DIR%/Platforms*}"
+    export DEVELOPER_DIR
     FRAMEWORKSHOME="$MACOSX_SDK_PATH/System/Library/Frameworks"
     MACOSX_DEPLOYMENT_TARGET="$with_macosx_version_min_required"