package/uClibc: ensure .config is writable

If $(UCLIBC_CONFIG_FILE) is read-only (eg. because Buildroot's
source dir is), the sed fixups to .config fail.

Signed-off-by: Nathan Lynch <ntl@pobox.com>
[yann.morin.1998@free.fr: use $(INSTALL) instead of cp]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/uclibc/uclibc.mk

@@ -414,7 +414,7 @@ UCLIBC_MAKE_FLAGS = \
 	HOSTCC="$(HOSTCC)"
 
 define UCLIBC_SETUP_DOT_CONFIG
-	cp -f $(UCLIBC_CONFIG_FILE) $(@D)/.config
+	$(INSTALL) -m 0644 $(UCLIBC_CONFIG_FILE) $(@D)/.config
 	$(call UCLIBC_OPT_SET,CROSS_COMPILER_PREFIX,"$(TARGET_CROSS)",$(@D))
 	$(call UCLIBC_OPT_SET,TARGET_$(UCLIBC_TARGET_ARCH),y,$(@D))
 	$(call UCLIBC_OPT_SET,TARGET_ARCH,"$(UCLIBC_TARGET_ARCH)",$(@D))