image: Fix do_install_imager_deps dependency

To allow the usage of imager with ISAR_CROSS_COMPILE set to "1" replace
hardcoded buildchroot-target dependency with proper one.

Signed-off-by: Anton Mikanovich <amikan@ilbers.de>

meta/classes/image-tools-extension.bbclass

@@ -14,7 +14,7 @@ IMAGER_INSTALL ??= ""
 IMAGER_BUILD_DEPS ??= ""
 DEPENDS += "${IMAGER_BUILD_DEPS}"
 
-do_install_imager_deps[depends] = "buildchroot-target:do_build"
+do_install_imager_deps[depends] = "${BUILDCHROOT_DEP}"
 do_install_imager_deps[deptask] = "do_deploy_deb"
 do_install_imager_deps[lockfiles] += "${REPO_ISAR_DIR}/isar.lock"
 do_install_imager_deps() {