Okay, that doesn't work either. Removing --with-sdk for now.

tools/tinderbox-configs/lightning/macosx/mozconfig

@@ -12,6 +12,5 @@ ac_add_options --disable-static
 ac_add_options --enable-shared
 ac_add_options --disable-tests
 ac_add_options --disable-debug
-ac_add_options --with-macos-sdk=/Developer/SDKs/MacOSX10.3.9.sdk
 # Use Carbon widgets, regardless of what trunk's default is
 ac_add_options --enable-default-toolkit=mac

tools/tinderbox-configs/sunbird/macosx/mozconfig

@@ -15,7 +15,6 @@ ac_add_options --disable-shared
 ac_add_options --disable-installer
 ac_add_options --disable-tests
 ac_add_options --enable-prebinding
-ac_add_options --with-macos-sdk=/Developer/SDKs/MacOSX10.3.9.sdk
 # Use Carbon widgets, regardless of what trunk's default is
 ac_add_options --enable-default-toolkit=mac
 # SVG now requires Cairo, so disable it for now.