Pass SDK root to the linker as -isysroot, not -Wl,-syslibroot

The former option to clang will result in more options to the linker,
such as the newly introduced -platform_version, which writes the
SDK version to the resulting binary. By using the syslibroot flag
directly we were missing the platform version, and binaries were
left without an SDK version set, resulting in failed validation
of the binary. Going with the clang driver gives us the right
behavior for free.

Fixes: QTBUG-83100
Change-Id: I98bc9ba644dae4bcc7a6a88481556bae185ce5fa
Reviewed-by: Simon Hausmann <[email protected]>
Reviewed-by: Timur Pocheptsov <[email protected]>
(cherry picked from commit 6a60192)
Reviewed-by: Tor Arne Vestbø <[email protected]>

configure

@@ -271,12 +271,9 @@ macSDKify()
                 val=$(echo $sdk_val $(echo $val | cut -s -d ' ' -f 2-))
                 echo "$var=$val"
             ;;
-            QMAKE_CFLAGS=*|QMAKE_CXXFLAGS=*)
+            QMAKE_CFLAGS=*|QMAKE_CXXFLAGS=*|QMAKE_LFLAGS=*)
                 echo "$line -isysroot $sysroot $version_min_flag"
             ;;
-            QMAKE_LFLAGS=*)
-                echo "$line -Wl,-syslibroot,$sysroot $version_min_flag"
-            ;;
             *)
                 echo "$line"
             ;;

mkspecs/features/mac/default_post.prf

@@ -198,7 +198,7 @@ macx-xcode {
                 -isysroot$$xcodeSDKInfo(Path, $$sdk)
             QMAKE_XARCH_LFLAGS_$${arch} = $$version_min_flags \
                 -Xarch_$${arch} \
-                -Wl,-syslibroot,$$xcodeSDKInfo(Path, $$sdk)
+                -isysroot$$xcodeSDKInfo(Path, $$sdk)
 
             QMAKE_XARCH_CFLAGS += $(EXPORT_QMAKE_XARCH_CFLAGS_$${arch})
             QMAKE_XARCH_LFLAGS += $(EXPORT_QMAKE_XARCH_LFLAGS_$${arch})
@@ -222,7 +222,7 @@ macx-xcode {
         version_min_flag = -m$${version_identifier}-version-min=$$deployment_target
         QMAKE_CFLAGS += -isysroot $$sysroot_path $$version_min_flag
         QMAKE_CXXFLAGS += -isysroot $$sysroot_path $$version_min_flag
-        QMAKE_LFLAGS += -Wl,-syslibroot,$$sysroot_path $$version_min_flag
+        QMAKE_LFLAGS += -isysroot $$sysroot_path $$version_min_flag
     }
 
     # Enable precompiled headers for multiple architectures