palemoon/installer: Fix packaging when built --with-system-nss/nspr

The variables set by 'configure' for --with-system-(nss|nspr) is named
differently in UXP. This breaks packaging for palemoon when system
nss/nspr is used.

This commit corrects the name of said variables.

application/palemoon/installer/Makefile.in

@@ -41,12 +41,12 @@ DEFINES += -DMOZ_GTK3=1
 endif
 endif
 
-ifdef MOZ_NATIVE_NSPR
-DEFINES += -DMOZ_NATIVE_NSPR=1
+ifdef MOZ_SYSTEM_NSPR
+DEFINES += -DMOZ_SYSTEM_NSPR=1
 endif
 
-ifdef MOZ_NATIVE_NSS
-DEFINES += -DMOZ_NATIVE_NSS=1
+ifdef MOZ_SYSTEM_NSS
+DEFINES += -DMOZ_SYSTEM_NSS=1
 endif
 
 ifdef NSS_DISABLE_DBM