build: fix incorrect initramfs bzip2 compression

Requires: tools/bzip2

fix consistency of executable to use `$(STAGING_DIR_HOST)/bin/bzip2`, and
not system-installed ones from the usual environment `PATH`;
this affects option `CONFIG_KERNEL_INITRAMFS_COMPRESSION_BZIP2`

this may have worked in the past but only via side effect of having the
binaries on the host system (and whatever unpredictable version or
patchset those might be)

Fixes: 330bd380e8b6 ("image: allow building FIT and uImage with ramdisk")
Signed-off-by: Tony Butler <[email protected]>

include/kernel-defaults.mk

@@ -177,7 +177,7 @@ else
 	( cd $(TARGET_DIR); find . | LC_ALL=C sort | $(STAGING_DIR_HOST)/bin/cpio --reproducible -o -H newc -R 0:0 > $(KERNEL_BUILD_DIR)/initrd.cpio )
 endif
 	$(if $(SOURCE_DATE_EPOCH),touch -hcd "@$(SOURCE_DATE_EPOCH)" $(KERNEL_BUILD_DIR)/initrd.cpio)
-	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_BZIP2),bzip2 -9 -c < $(KERNEL_BUILD_DIR)/initrd.cpio > $(KERNEL_BUILD_DIR)/initrd.cpio.bzip2)
+	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_BZIP2),$(STAGING_DIR_HOST)/bin/bzip2 -9 -c < $(KERNEL_BUILD_DIR)/initrd.cpio > $(KERNEL_BUILD_DIR)/initrd.cpio.bzip2)
 	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_GZIP),gzip -n -f -S .gzip -9n $(KERNEL_BUILD_DIR)/initrd.cpio)
 	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_LZ4),$(STAGING_DIR_HOST)/bin/lz4c -l -c1 -fz --favor-decSpeed $(KERNEL_BUILD_DIR)/initrd.cpio)
 	$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_LZMA),$(STAGING_DIR_HOST)/bin/lzma e -lc1 -lp2 -pb2 $(KERNEL_BUILD_DIR)/initrd.cpio $(KERNEL_BUILD_DIR)/initrd.cpio.lzma)