qmake: fix MAKEFLAGS when PARALLEL_MAKE has space

* quotes are needed, because some people have '-j 9' instead of '-j9'
* this can in theory cause PARALLEL_MAKE x PARALLEL_MAKE threads, because
  MAKE itself is using PARALLEL_MAKE threads to run inner makes

classes/qmake5_base.bbclass

@@ -2,7 +2,7 @@ QMAKE_MKSPEC_PATH ?= "${STAGING_DATADIR_NATIVE}/${QT_DIR_NAME}/mkspecs"
 OE_QMAKE_PLATFORM = "${TARGET_OS}-oe-g++"
 QMAKESPEC := "${QMAKE_MKSPEC_PATH}/${OE_QMAKE_PLATFORM}"
 
-EXTRA_OEMAKE = ' MAKEFLAGS=${PARALLEL_MAKE} '
+EXTRA_OEMAKE = " MAKEFLAGS='${PARALLEL_MAKE}'"
 
 EXTRA_ENV = 'QMAKE="${OE_QMAKE_QMAKE} -d -after \
              INCPATH+=${STAGING_INCDIR}/freetype2 LIBS+=-L${STAGING_LIBDIR}" \

recipes-qt/qt5/qtbase-native.inc

@@ -18,7 +18,7 @@ SRC_URI += " \
 "
 
 EXTRA_ENV = 'MAKE="make -e ${PARALLEL_MAKE}"'
-EXTRA_OEMAKE = ' MAKEFLAGS=${PARALLEL_MAKE} '
+EXTRA_OEMAKE = " MAKEFLAGS='${PARALLEL_MAKE}'"
 
 EXTRA_OECONF = " \
   -prefix ${prefix} \