Fix compilation with multiple rpath directories

Iterate over all diectories specified in QMAKE_RPATHDIR and generate a
rpath linker argument for each directory.

Change-Id: I90948eee9ef9319017ce99138ae7146d50c9636a
Reviewed-by: Michael Bruning <michael.bruning@digia.com>
Reviewed-by: Pierre Rossi <pierre.rossi@gmail.com>

build/qmake/mkspecs/features/gyp_generator.prf

@@ -79,7 +79,7 @@ for (library, LIBRARIES): LIBS -= "$$library"
 
 GYP_CONTENTS += "    'ldflags': ["
 for (lib, LIBS): GYP_CONTENTS += "      '$$lib',"
-!isEmpty(QMAKE_RPATHDIR): GYP_CONTENTS += "      '$$QMAKE_RPATH$$QMAKE_RPATHDIR',"
+for (rpath, QMAKE_RPATHDIR): GYP_CONTENTS += "      '$$QMAKE_RPATH$$rpath',"
 GYP_CONTENTS += "    ],"
 
 !isEmpty(QMAKE_CFLAGS) {