Update README.md: ppc linking again

fixes #30

Author: devernay

README.md

@@ -89,14 +89,24 @@ Here are the latest versions of Xcode that are known to /run/ on each OS X versi
 
 More information about the compilers included in each version of Xcode can be found on the [MacPorts Wiki](https://trac.macports.org/wiki/XcodeVersionInfo).
 
-### Linking on Xcode 7.3 and later
+### Linking for ppc on Xcode 7.3 and later
 
 The following error may appear when linking a program using the older compilers from Xcode (command-line and Makefile-based builds should not be affected):
 ```
 Running ld for ppc ...
+ld: unknown option: -object_path_lto
+```
+or
+```
+Running ld for ppc ...
 ld: unknown option: -no_deduplicate
 ```
-The reason is that the newer versions of the linker introduced the option `-no_deduplicate`, which Xcode adds by default. To disable this, add a User-Defined build setting in Xcode named `LD_DONT_RUN_DEDUPLICATION` and set its value to `NO`.
+The reason is that the newer versions of the linker introduced the options `-object_path_lto` and `-no_deduplicate`, which Xcode adds by default. To disable this, add the following two User-Defined build setting in Xcode (by clicking on the `+` at the to of the right column in the Build Settings panel):
+
+- `LD_LTO_OBJECT_FILE` with an empty value
+- `LD_DONT_RUN_DEDUPLICATION` with value set to `NO`.
+
+For future reference, other settings that control the link options are located in: `/Applications/Xcode.app/Contents/PlugIns/Xcode3Core.ideplugin/Contents/SharedSupport/Developer/Library/Xcode/Plug-ins/CoreBuildTasks.xcplugin/Contents/Resources/Ld.xcspec`
 
 Known bugs (and fixes) in OS X SDKs
 -----------------------------------