complain about various invalid configuration attempts

Task-number: QTBUG-56049
Change-Id: Id5eeb014c2b88195d2d14566a62dcb9185206b37
Reviewed-by: Jake Petroules <jake.petroules@qt.io>
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

configure

@@ -82,6 +82,11 @@ if [ x"$1" = x"-top-level" ]; then
     relpathMangled=`dirname "$relpath"`
     outpathPrefix=../
     shift
+else
+    if [ -f ../.qmake.super ]; then
+        echo >&2 "ERROR: You cannot configure qtbase separately within a top-level build."
+        exit 1
+    fi
 fi
 
 OPT_CMDLINE=  # expanded version for the script

configure.bat

@@ -46,7 +46,12 @@ for %%P in ("%TOPQTSRC%") do set TOPQTSRC=%%~dpP
 set TOPQTSRC=%TOPQTSRC:~0,-1%
 for %%P in ("%QTDIR%") do set TOPQTDIR=%%~dpP
 set TOPQTDIR=%TOPQTDIR:~0,-1%
+goto wastoplevel
 :notoplevel
+if not exist ..\.qmake.super goto wastoplevel
+echo ERROR: You cannot configure qtbase separately within a top-level build. >&2
+exit /b 1
+:wastoplevel
 
 set SYNCQT=
 set PLATFORM=

mkspecs/features/qt_configure.prf

@@ -1700,6 +1700,14 @@ defineTest(qtConfProcessOutput) {
 
 !isEmpty(_QMAKE_SUPER_CACHE_):!equals(OUT_PWD, $$dirname(_QMAKE_SUPER_CACHE_)) {
     # sub-repo within a top-level build; no need to configure anything.
+    !isEmpty(QMAKE_EXTRA_ARGS) {
+        # sub-projects don't get the extra args passed down automatically,
+        # so we can use their presence to detect misguided attempts to
+        # configure the repositories separately.
+        # caveat: a plain qmake call is indistinguishable from a recursion
+        # (by design), so we cannot detect this case.
+        error("You cannot configure $$TARGET separately within a top-level build.")
+    }
     return()
 }
 
@@ -1717,8 +1725,11 @@ for (c, cfgs) {
     exists($$s/configure.json): \
         configsToProcess += $$c
 }
-isEmpty(configsToProcess): \
+isEmpty(configsToProcess) {
+    !isEmpty(QMAKE_EXTRA_ARGS): \
+        error("This module does not accept configure command line arguments.")
     return()
+}
 
 load(configure_base)