Mac: Use rpath instead of executable_path.

Because executable_path and loader_path are just too inflexible for some
stuff. The rpath is supposed to be set to the Qt Creator app's Contents
folder.
Compiling on 10.4 now requires to enter compatibility mode via
QTC_TIGER_COMPAT env variable or TIGER_COMPAT_MODE qmake variable.

qtcreator.pri

@@ -99,6 +99,7 @@ macx {
     IDE_BIN_PATH     = $$IDE_APP_PATH/$${IDE_APP_TARGET}.app/Contents/MacOS
     contains(QT_CONFIG, ppc):CONFIG += ppc x86
     copydata = 1
+    isEmpty(TIGER_COMPAT_MODE):TIGER_COMPAT_MODE=$$(QTC_TIGER_COMPAT)
 } else {
     win32 {
         contains(TEMPLATE, vc.*)|contains(TEMPLATE_PREFIX, vc):vcproj = 1

src/qtcreatorplugin.pri

@@ -28,7 +28,12 @@ QMAKE_EXTRA_COMPILERS += copy2build
 
 
 macx {
+    !isEmpty(TIGER_COMPAT_MODE) {
         QMAKE_LFLAGS_SONAME = -Wl,-install_name,@executable_path/../PlugIns/$${PROVIDER}/
+    } else {
+        QMAKE_LFLAGS_SONAME = -Wl,-install_name,@rpath/PlugIns/$${PROVIDER}/
+        QMAKE_LFLAGS += -Wl,-rpath,@loader_path/../../
+    }
 } else:linux-* {
     #do the rpath by hand since it's not possible to use ORIGIN in QMAKE_RPATHDIR
     QMAKE_RPATHDIR += \$\$ORIGIN

src/rpath.pri

 macx {
-    QMAKE_LFLAGS_SONAME = -Wl,-install_name,@executable_path/../PlugIns/
+    !isEmpty(TIGER_COMPAT_MODE) {
+        QMAKE_LFLAGS_SONAME = -Wl,-install_name,@executable_path/../PlugIns/
+    } else {
+        QMAKE_LFLAGS_SONAME = -Wl,-install_name,@rpath/PlugIns/
+        QMAKE_LFLAGS += -Wl,-rpath,@loader_path/../
+    }
 } else:linux-* {
     #do the rpath by hand since it's not possible to use ORIGIN in QMAKE_RPATHDIR
     # this expands to $ORIGIN (after qmake and make), it does NOT read a qmake var