qtbase: fix install if lcl_maybe_fortify is empty

lcl_maybe_fortify might be empty, which would make sed fail during
do_install. Workaround this by adding space to the substitution
pattern.

Fixes: QTBUG-115588
Pick-to: 6.6 6.5 6.2
Change-Id: Ic6c5a6c80011dfefc92e1b2d7aadc48cce82ed7a
Reviewed-by: Ari Parkkila <ari.parkkila@qt.io>

recipes-qt/qt6/qtbase_git.bb

@@ -208,7 +208,7 @@ EOF
 
 do_install:append:class-target() {
     sed >> ${D}${QT6_INSTALL_MKSPECSDIR}/linux-oe-g++/qmake.conf <<EOF \
-        -e 's:${lcl_maybe_fortify}::' \
+        -e 's: ${lcl_maybe_fortify}: :' \
         -e 's:${DEBUG_PREFIX_MAP}::' \
         -e 's:${RECIPE_SYSROOT}:$$[QT_SYSROOT]:' \
         -e 's:${TARGET_PREFIX}:$$[QT_HOST_PREFIX]${bindir}/${TARGET_SYS}/${TARGET_PREFIX}:'