openpower/petitboot: Export PETITBOOT_VERSION to autoconf

Petitboot determines its version string at autoreconf; export
PETITBOOT_VERSION so that Petitboot can inherit the version string
created by op-build.

Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
diff --git a/openpower/package/petitboot/petitboot.mk b/openpower/package/petitboot/petitboot.mk
index 55f04b3..8e9782e 100644
--- a/openpower/package/petitboot/petitboot.mk
+++ b/openpower/package/petitboot/petitboot.mk
@@ -19,6 +19,8 @@
 	      HOST_PROG_SHUTDOWN=/usr/libexec/petitboot/bb-kexec-reboot \
 	      $(if $(BR2_PACKAGE_BUSYBOX),--with-tftp=busybox)
 
+PETITBOOT_AUTORECONF_ENV += PETITBOOT_VERSION=`cat $(PETITBOOT_VERSION_FILE) | cut -d '-' -f 2-`
+
 ifdef PETITBOOT_DEBUG
 PETITBOOT_CONF_OPTS += --enable-debug
 endif