[Buildroot] [PATCH] linux: use host pkg-config when host libelf is set

[Stuart Summers <stuart.summers@intel.com>]

A patch was added to the Linux kernel in 5.1.0-rc3 which
adds a requirement that the host build environment include
pkg-config. Add the correct host-pkgconf dependency and
environment variables to ensure Linux picks up the correct
libraries.

Suggested-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Stuart Summers <stuart.summers@intel.com>
---
 linux/linux.mk | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/linux/linux.mk b/linux/linux.mk
index 6bf2b88038..05bb5b9525 100644
--- a/linux/linux.mk
+++ b/linux/linux.mk
@@ -96,10 +96,6 @@ ifeq ($(BR2_LINUX_KERNEL_NEEDS_HOST_OPENSSL),y)
 LINUX_DEPENDENCIES += host-openssl
 endif
 
-ifeq ($(BR2_LINUX_KERNEL_NEEDS_HOST_LIBELF),y)
-LINUX_DEPENDENCIES += host-elfutils
-endif
-
 # If host-uboot-tools is selected by the user, assume it is needed to
 # create a custom image
 ifeq ($(BR2_PACKAGE_HOST_UBOOT_TOOLS),y)
@@ -125,6 +121,16 @@ LINUX_MAKE_ENV = \
 	$(TARGET_MAKE_ENV) \
 	BR_BINARIES_DIR=$(BINARIES_DIR)
 
+ifeq ($(BR2_LINUX_KERNEL_NEEDS_HOST_LIBELF),y)
+LINUX_DEPENDENCIES += host-elfutils host-pkgconf
+LINUX_MAKE_ENV += \
+	PKG_CONFIG="$(PKG_CONFIG_HOST_BINARY)" \
+	PKG_CONFIG_SYSROOT_DIR="/" \
+	PKG_CONFIG_ALLOW_SYSTEM_CFLAGS=1 \
+	PKG_CONFIG_ALLOW_SYSTEM_LIBS=1 \
+	PKG_CONFIG_LIBDIR="$(HOST_DIR)/lib/pkgconfig:$(HOST_DIR)/share/pkgconfig"
+endif
+
 ifeq ($(BR2_REPRODUCIBLE),y)
 LINUX_MAKE_ENV += \
 	KBUILD_BUILD_VERSION=1 \
-- 
2.20.1