Revert "bzip2/xz: use the prebuilts."

This reverts commit e114b3f0a9.

Build broke as follows:

out/soong/host/linux-x86/bin/sbox --sandbox-path out/soong/.temp --output-root out/soong/.intermediates/system/update_engine/ue_unittest_disk_imgs/gen -c 'tar -jxf system/update_engine/sample_images/sample_images.tar.bz2 -C __SBOX_OUT_DIR__/gen disk_ext2_1k.img disk_ext2_4k.img disk_ext2_4k_empty.img disk_ext2_unittest.img' __SBOX_OUT_DIR__/gen/disk_ext2_1k.img __SBOX_OUT_DIR__/gen/disk_ext2_4k.img __SBOX_OUT_DIR__/gen/disk_ext2_4k_empty.img __SBOX_OUT_DIR__/gen/disk_ext2_unittest.img 
"bzip2" is not allowed to be used. See https://android.googlesource.com/platform/build/+/master/Changes.md#PATH_Tools for more information. 
tar: Child returned status 1 
tar: Error is not recoverable: exiting now 
sbox command (tar -jxf system/update_engine/sample_images/sample_images.tar.bz2 -C out/soong/.temp/sbox849645882/gen disk_ext2_1k.img disk_ext2_4k.img disk_ext2_4k_empty.img disk_ext2_unittest.img) failed with err "exit status 2" 

Change-Id: I3fe7100886ea3b748f5a6b5fc6d2811391bb72a8

ui/build/paths/config.go

@@ -76,6 +76,7 @@ func GetConfig(name string) PathConfig {
 var Configuration = map[string]PathConfig{
 	"bash":     Allowed,
 	"bc":       Allowed,
+	"bzip2":    Allowed,
 	"date":     Allowed,
 	"dd":       Allowed,
 	"diff":     Allowed,
@@ -103,6 +104,7 @@ var Configuration = map[string]PathConfig{
 	"timeout":  Allowed,
 	"tr":       Allowed,
 	"unzip":    Allowed,
+	"xz":       Allowed,
 	"zip":      Allowed,
 	"zipinfo":  Allowed,