Fix AC_PATH_PROGS for cygwin and msys2

Fixes searching for native qt5 progs on cygwin and msys2

The reason for the issue is that on windows if there is a space in the path
or if the program is prepends with .exe and we specify the search PATH
in AC_PATH_PROGS we must enclose them in quotes or the program will not be
found.

For future reference, if anyone uses AC_PATH_PROGS please enclose defined
search paths (if you have any) in quotes
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

configure.ac

@@ -3798,9 +3798,9 @@ AS_IF([test "${enable_qt}" != "no"], [
       ])
       QT_PATH="$(eval $PKG_CONFIG --variable=exec_prefix Qt5Core)"
       QT_HOST_PATH="$(eval $PKG_CONFIG --variable=host_bins Qt5Core)"
-      AC_PATH_PROGS(MOC, [moc-qt5 moc], moc, [${QT_HOST_PATH} ${QT_PATH}/bin ${CONTRIB_DIR}/bin])
-      AC_PATH_PROGS(RCC, [rcc-qt5 rcc], rcc, [${QT_HOST_PATH} ${QT_PATH}/bin ${CONTRIB_DIR}/bin])
-      AC_PATH_PROGS(UIC, [uic-qt5 uic], uic, [${QT_HOST_PATH} ${QT_PATH}/bin ${CONTRIB_DIR}/bin])
+      AC_PATH_PROGS(MOC, [moc-qt5 moc], moc, ["${QT_HOST_PATH}" "${QT_PATH}/bin" "${CONTRIB_DIR}/bin"])
+      AC_PATH_PROGS(RCC, [rcc-qt5 rcc], rcc, ["${QT_HOST_PATH}" "${QT_PATH}/bin" "${CONTRIB_DIR}/bin"])
+      AC_PATH_PROGS(UIC, [uic-qt5 uic], uic, ["${QT_HOST_PATH}" "${QT_PATH}/bin" "${CONTRIB_DIR}/bin"])
     ], [
       PKG_CHECK_MODULES([QT], [QtCore QtGui >= 4.6.0],, [
         AS_IF([test -n "${enable_qt}"],[
@@ -3811,9 +3811,9 @@ AS_IF([test "${enable_qt}" != "no"], [
         enable_qt="no"
       ])
       QT_PATH="$(eval $PKG_CONFIG --variable=exec_prefix QtCore)"
-      AC_PATH_PROGS(MOC, [moc-qt4 moc], moc, [${QT_PATH}/bin ${CONTRIB_DIR}/bin])
+      AC_PATH_PROGS(MOC, [moc-qt4 moc], moc, ["${QT_PATH}/bin" "${CONTRIB_DIR}/bin"])
       AC_PATH_PROG(RCC, rcc, rcc, [${QT_PATH}/bin ${CONTRIB_DIR}/bin])
-      AC_PATH_PROGS(UIC, [uic-qt4 uic], uic, [${QT_PATH}/bin ${CONTRIB_DIR}/bin])
+      AC_PATH_PROGS(UIC, [uic-qt4 uic], uic, ["${QT_PATH}/bin" "${CONTRIB_DIR}/bin"])
     ])
 ])
 AS_IF([test "${enable_qt}" != "no"], [