package/qt5/qt5base: enable ccache via configure option

This should be cleaner than editing mkspecs/common/g++-base.conf.

This should be more reliable with qt5webengine gn build system.

Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
[Peter: Leave in QMAKE_{CC,CXX} override to ensure HOST{CC,CXX} is used]
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/qt5/qt5base/qt5base.mk

@@ -318,9 +318,14 @@ endef
 endif
 
 # This allows to use ccache when available
+ifeq ($(BR2_CCACHE),y)
+QT5BASE_CONFIGURE_OPTS += -ccache
+endif
+
+# Ensure HOSTCC/CXX is used
 define QT5BASE_CONFIGURE_HOSTCC
-	$(SED) 's,^QMAKE_CC\s*=.*,QMAKE_CC = $(HOSTCC),' $(@D)/mkspecs/common/g++-base.conf
-	$(SED) 's,^QMAKE_CXX\s*=.*,QMAKE_CXX = $(HOSTCXX),' $(@D)/mkspecs/common/g++-base.conf
+	$(SED) 's,^QMAKE_CC\s*=.*,QMAKE_CC = $(HOSTCC_NOCCACHE),' $(@D)/mkspecs/common/g++-base.conf
+	$(SED) 's,^QMAKE_CXX\s*=.*,QMAKE_CXX = $(HOSTCXX_NOCCACHE),' $(@D)/mkspecs/common/g++-base.conf
 endef
 
 # Must be last so can override all options set by Buildroot