Fastboot: use flash erase & logical block size for building userdata

If the bootloader provides erase-block-size and logical-block-size
getvar variables, then pass these to libext4_utils when building a new
userdata image. This info is used to tune stride and stripe-width.

Bug: 33243520
Test: Modify fb_getvar to return values for "erase-block-size" and
"logical-block-size" and check that fastboot -w sets userdata
parameters correctly.
Signed-off-by: Connor O'Brien <connoro@google.com>

Change-Id: Id48b7a3ebb9074983a4422a79a64dcb437c0f888
diff --git a/fastboot/fs.h b/fastboot/fs.h
index 0a68507..0a5f5a4 100644
--- a/fastboot/fs.h
+++ b/fastboot/fs.h
@@ -8,6 +8,6 @@
 
 const struct fs_generator* fs_get_generator(const std::string& fs_type);
 int fs_generator_generate(const struct fs_generator* gen, int tmpFileNo, long long partSize,
-    const std::string& initial_dir);
+    const std::string& initial_dir, unsigned eraseBlkSize = 0, unsigned logicalBlkSize = 0);
 
 #endif