genericx86: wic wks do not hardcode loader

replace .wks with .wks.in and refer loader to EFI_PROVIDER
to enable different bootloader.
soft assign default EFI_PROVIDER "grub-efi" for genericx86.

(From meta-yocto rev: 11ecd2febed95e923c8cc68e2c438cd846a88d02)

Signed-off-by: Chee Yang Lee <chee.yang.lee@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta-yocto-bsp/conf/machine/include/genericx86-common.inc

@@ -20,6 +20,7 @@ GLIBC_ADDONS = "nptl"
 EXTRA_OECONF_append_pn-matchbox-panel-2 = " --with-battery=acpi"
 
 IMAGE_FSTYPES += "wic wic.bmap"
-WKS_FILE ?= "genericx86.wks"
+WKS_FILE ?= "genericx86.wks.in"
+EFI_PROVIDER ??= "grub-efi"
 do_image_wic[depends] += "gptfdisk-native:do_populate_sysroot"
 do_image_wic[recrdeptask] += "do_bootimg"

meta-yocto-bsp/wic/genericx86.wks → meta-yocto-bsp/wic/genericx86.wks.in

@@ -1,6 +1,6 @@
 # short-description: Create an EFI disk image for genericx86*
 # long-description: Creates a partitioned EFI disk image for genericx86* machines
-part /boot --source bootimg-efi --sourceparams="loader=grub-efi" --ondisk sda --label msdos --active --align 1024
+part /boot --source bootimg-efi --sourceparams="loader=${EFI_PROVIDER}" --ondisk sda --label msdos --active --align 1024
 part / --source rootfs --ondisk sda --fstype=ext4 --label platform --align 1024 --use-uuid
 part swap --ondisk sda --size 44 --label swap1 --fstype=swap