fix OSX 10.9 compiler/stdlib override for latest homebrew

docs/installation.md

@@ -126,15 +126,19 @@ For each of these formulas, `brew edit FORMULA`, and add the ENV definitions as
 
 ```
     def install
-        #ADD THE FOLLOWING:
-        ENV.append "CXXFLAGS", '-stdlib=libstdc++'
-        ENV.append "CFLAGS", '-stdlib=libstdc++'
-        ENV.append "LDFLAGS", '-stdlib=libstdc++ -lstdc++'
-        #The following is necessary because libtool liks to strip LDFLAGS:
-        ENV.cxx = "/usr/bin/clang -stdlib=libstdc++"
+        # ADD THE FOLLOWING:
+        ENV.append "CXXFLAGS", "-stdlib=libstdc++"
+        ENV.append "CFLAGS", "-stdlib=libstdc++"
+        ENV.append "LDFLAGS", "-stdlib=libstdc++ -lstdc++"
+        # The following is necessary because libtool likes to strip LDFLAGS:
+        ENV["CXX"] = "/usr/bin/clang -stdlib=libstdc++"
         ...
 ```
 
+To edit the formulae in turn, run
+
+    for x in snappy leveldb protobuf gflags glog szip boost homebrew/science/opencv; do brew edit $x; done
+
 After this, run
 
     for x in snappy leveldb protobuf gflags glog szip boost homebrew/science/opencv; do brew uninstall $x; brew install --build-from-source --fresh -vd $x; done