qextserialport: use TARGET_MAKE_ENV when running make and qmake

This patch prepends TARGET_MAKE_ENV to $(MAKE) and $(QT_QMAKE) command
lines, to make sure PATH is set correctly, and to line up with the qt5
packages that do this consistently.

Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/qextserialport/qextserialport.mk

@@ -15,11 +15,11 @@ QEXTSERIALPORT_DEPENDENCIES = qt
 QEXTSERIALPORT_INSTALL_STAGING = YES
 
 define QEXTSERIALPORT_CONFIGURE_CMDS
-	(cd $(@D); $(QT_QMAKE))
+	(cd $(@D); $(TARGET_MAKE_ENV) $(QT_QMAKE))
 endef
 
 define QEXTSERIALPORT_BUILD_CMDS
-	$(MAKE) -C $(@D)
+	$(TARGET_MAKE_ENV) $(MAKE) -C $(@D)
 endef
 
 define QEXTSERIALPORT_INSTALL_STAGING_CMDS