linux: add BR2_LINUX_KERNEL_NEEDS_HOST_LIBELF

Some Linux kernel configuration options (such as CONFIG_UNWINDER_ORC)
require building a host program that needs libelf.

Users who have libelf installed on their system won't see a problem,
but users who don't have libelf installed will get a build
failure. Therefore, this commit adds an option that allows a user to
indicate that his Linux kernel configuration requires libelf. When
this option is enabled, we add host-elfutils to the dependencies of
the linux package (host-elfutils provides the libelf library).

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

linux/Config.in

@@ -420,6 +420,19 @@ config BR2_LINUX_KERNEL_NEEDS_HOST_OPENSSL
 	  such as "scripts/extract-cert.c:21:25: fatal error:
 	  openssl/bio.h: No such file or directory".
 
+config BR2_LINUX_KERNEL_NEEDS_HOST_LIBELF
+	bool "Needs host libelf"
+	help
+	  Some Linux kernel configuration options (such as
+	  CONFIG_UNWINDER_ORC) require building a host program that
+	  needs libelf. Enabling this option will ensure host-elfutils
+	  (which provides libelf) gets built before the Linux kernel.
+
+	  Enable this option if you get a Linux kernel build failure
+	  such as "Cannot generate ORC metadata for
+	  CONFIG_UNWINDER_ORC=y, please install libelf-dev,
+	  libelf-devel or elfutils-libelf-devel".
+
 # Linux extensions
 source "linux/Config.ext.in"
 

linux/linux.mk

@@ -84,6 +84,10 @@ 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)