xcode_emulation: work in the absence of xcodebuild

pylib/gyp/xcode_emulation.py

Index: pylib/gyp/xcode_emulation.py
diff --git a/pylib/gyp/xcode_emulation.py b/pylib/gyp/xcode_emulation.py
index b2aab986a427d5285d70558bf97f0a42bfe1556e..20592c73fae660009aac621097cf3c4fb61d6cb6 100644
--- a/pylib/gyp/xcode_emulation.py
+++ b/pylib/gyp/xcode_emulation.py
@@ -236,8 +236,14 @@ class XcodeSettings(object):
     if sdk_root.startswith('/'):
       return sdk_root
     if sdk_root not in XcodeSettings._sdk_path_cache:
-      XcodeSettings._sdk_path_cache[sdk_root] = self._GetSdkVersionInfoItem(
-          sdk_root, 'Path')
+      try:
+        XcodeSettings._sdk_path_cache[sdk_root] = self._GetSdkVersionInfoItem(
+            sdk_root, 'Path')
+      except:
+        # if this fails it's because xcodebuild failed, which means
+        # the user is probably on a CLT-only system, where there
+        # is no valid SDK root
+        XcodeSettings._sdk_path_cache[sdk_root] = None
     return XcodeSettings._sdk_path_cache[sdk_root]
 
   def _AppendPlatformVersionMinFlags(self, lst):
@@ -340,10 +346,11 @@ class XcodeSettings(object):
 
     cflags += self._Settings().get('WARNING_CFLAGS', [])
 
-    config = self.spec['configurations'][self.configname]
-    framework_dirs = config.get('mac_framework_dirs', [])
-    for directory in framework_dirs:
-      cflags.append('-F' + directory.replace('$(SDKROOT)', sdk_root))
+    if sdk_root:
+      config = self.spec['configurations'][self.configname]
+      framework_dirs = config.get('mac_framework_dirs', [])
+      for directory in framework_dirs:
+        cflags.append('-F' + directory.replace('$(SDKROOT)', sdk_root))
 
     self.configname = None
     return cflags
@@ -573,10 +580,11 @@ class XcodeSettings(object):
     for rpath in self._Settings().get('LD_RUNPATH_SEARCH_PATHS', []):
       ldflags.append('-Wl,-rpath,' + rpath)
 
-    config = self.spec['configurations'][self.configname]
-    framework_dirs = config.get('mac_framework_dirs', [])
-    for directory in framework_dirs:
-      ldflags.append('-F' + directory.replace('$(SDKROOT)', self._SdkPath()))
+    if self._SdkPath():
+      config = self.spec['configurations'][self.configname]
+      framework_dirs = config.get('mac_framework_dirs', [])
+      for directory in framework_dirs:
+        ldflags.append('-F' + directory.replace('$(SDKROOT)', self._SdkPath()))
 
     self.configname = None
     return ldflags
@@ -701,7 +709,10 @@ class XcodeSettings(object):
         l = '-l' + m.group(1)
       else:
         l = library
-    return l.replace('$(SDKROOT)', self._SdkPath())
+    if self._SdkPath():
+      return l.replace('$(SDKROOT)', self._SdkPath())
+    else:
+      return l
 
   def AdjustLibraries(self, libraries):
     """Transforms entries like 'Cocoa.framework' in libraries into entries like