diff --git mkspecs/common/clang-mac.conf mkspecs/common/clang-mac.conf
index 14340630..a98aa869 100644
--- mkspecs/common/clang-mac.conf
+++ mkspecs/common/clang-mac.conf
@@ -7,8 +7,8 @@ QMAKE_OBJCXXFLAGS_USE_PRECOMPILE = $$QMAKE_CFLAGS_USE_PRECOMPILE
 QMAKE_XCODE_GCC_VERSION = com.apple.compilers.llvm.clang.1_0
 QMAKE_LFLAGS_LTCG_SEPARATE_DEBUG_INFO = -Wl,-object_path_lto,${OBJECTS_DIR}/${TARGET}_lto.o
 
-QMAKE_CXXFLAGS += -stdlib=libc++
-QMAKE_LFLAGS   += -stdlib=libc++
+QMAKE_CXXFLAGS += -stdlib=__MACPORTS_CXX_STDLIB__
+QMAKE_LFLAGS   += -stdlib=__MACPORTS_CXX_STDLIB__
 QMAKE_AR_LTCG  = libtool -static -o
 
 QMAKE_CFLAGS_APPLICATION_EXTENSION  = -fapplication-extension
diff --git mkspecs/common/clang.conf mkspecs/common/clang.conf
index dad15a22..8a30113e 100644
--- mkspecs/common/clang.conf
+++ mkspecs/common/clang.conf
@@ -4,8 +4,8 @@
 
 QMAKE_COMPILER          = gcc clang llvm   # clang pretends to be gcc
 
-QMAKE_CC                = $${CROSS_COMPILE}clang
-QMAKE_CXX               = $${CROSS_COMPILE}clang++
+QMAKE_CC                = __MACPORTS_CC__
+QMAKE_CXX               = __MACPORTS_CXX__
 
 QMAKE_LINK_C            = $$QMAKE_CC
 QMAKE_LINK_C_SHLIB      = $$QMAKE_CC
diff --git mkspecs/common/gcc-base.conf mkspecs/common/gcc-base.conf
index 99d77156..2e124369 100644
--- mkspecs/common/gcc-base.conf
+++ mkspecs/common/gcc-base.conf
@@ -34,7 +34,7 @@
 QMAKE_CFLAGS_OPTIMIZE      = -O2
 QMAKE_CFLAGS_OPTIMIZE_FULL = -O3
 QMAKE_CFLAGS_OPTIMIZE_DEBUG = -Og
-QMAKE_CFLAGS_OPTIMIZE_SIZE = -Os
+QMAKE_CFLAGS_OPTIMIZE_SIZE = __MACPORTS_OPTFLAGS__
 
 !equals(QMAKE_HOST.os, Windows): QMAKE_CFLAGS += -pipe
 QMAKE_CFLAGS_DEPS          += -M
diff --git mkspecs/common/macx.conf mkspecs/common/macx.conf
index 4ba0a8ea..5f75283f 100644
--- mkspecs/common/macx.conf
+++ mkspecs/common/macx.conf
@@ -3,9 +3,10 @@
 #
 
 QMAKE_PLATFORM         += macos osx macx
-QMAKE_MAC_SDK           = macosx
+QMAKE_MAC_SDK           = __MACPORTS_MAC_SDK__
 
-QMAKE_MACOSX_DEPLOYMENT_TARGET = 10.13
+QMAKE_MACOSX_DEPLOYMENT_TARGET = __MACPORTS_DEPLOYMENT_TARGET__
+QMAKE_APPLE_DEVICE_ARCHS = __MACPORTS_DEVICE_ARCHS__
 
 # Should be 10.15, but as long as the CI builds with
 # older SDKs we have to keep this.
diff --git mkspecs/macx-clang/qmake.conf mkspecs/macx-clang/qmake.conf
index 0cf1f31b..73752938 100644
--- mkspecs/macx-clang/qmake.conf
+++ mkspecs/macx-clang/qmake.conf
@@ -21,8 +21,8 @@
 # and X11, OpenGL is currently not supported.
 
 QMAKE_LIBS_X11 = -lX11 -lXext -lm
-QMAKE_LIBDIR_X11 = /opt/X11/lib
-QMAKE_INCDIR_X11 = /opt/X11/include
+QMAKE_LIBDIR_X11 = __MACPORTS_PREFIX__/lib
+QMAKE_INCDIR_X11 = __MACPORTS_PREFIX__/include
 
 include(../common/macx.conf)
 include(../common/gcc-base-mac.conf)