package/grep: install to /bin to fix busybox aliasing

When the grep package is selected, it should be installed at the same exact
location where busybox installs it too, this way the grep/egrep/fgrep
executables will end up overwriting the busybox provided ones.

Signed-off-by: Angelo Compagnucci <angelo@amarulasolutions.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit 10bc79c612dd945af236f23e11b4df79b3c76257)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/grep/grep.mk

@@ -10,6 +10,8 @@ GREP_SOURCE = grep-$(GREP_VERSION).tar.xz
 GREP_LICENSE = GPL-3.0+
 GREP_LICENSE_FILES = COPYING
 GREP_DEPENDENCIES = $(TARGET_NLS_DEPENDENCIES)
+# install into /bin like busybox grep
+GREP_CONF_OPTS = --exec-prefix=/
 
 # link with iconv if enabled
 ifeq ($(BR2_PACKAGE_LIBICONV),y)