package/runc: use BR_PATH to find pkg-config

When BR2_PACKAGE_LIBSECCOMP is set, go will try to find libseccomp
library using pkg-config. But pkg-config is not in the PATH when go
is called during the runc build.

Set the correct PATH in RUNC_MAKE_ENV.

Fixes:
http://autobuild.buildroot.net/results/fea/fea069fec671b32bffd3d133898d71d45abab552

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Cc: Christian Stewart <christian@paral.in>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/runc/runc.mk

@@ -15,7 +15,8 @@ RUNC_GOPATH = "$(@D)/Godeps/_workspace"
 RUNC_MAKE_ENV = $(HOST_GO_TARGET_ENV) \
 	CGO_ENABLED=1 \
 	GOBIN="$(@D)/bin" \
-	GOPATH="$(RUNC_GOPATH)"
+	GOPATH="$(RUNC_GOPATH)" \
+	PATH=$(BR_PATH)
 
 RUNC_GLDFLAGS = \
 	-X main.gitCommit=$(RUNC_VERSION) \