releasetools: Kill the use of os.getenv('AVBTOOL').

OTA tools should pick up the avbtool, as listed in dict['avb_avbtool'],
from the current PATH (plus bin/ under the dir specified via `--path`),
the same way as handling all other host tools.

Test: `m dist`
Change-Id: I3eb4d2c61979b03d9c23b2403d9a38cf052d87ea
diff --git a/tools/releasetools/add_img_to_target_files.py b/tools/releasetools/add_img_to_target_files.py
index 5132ae7..46dd416 100755
--- a/tools/releasetools/add_img_to_target_files.py
+++ b/tools/releasetools/add_img_to_target_files.py
@@ -260,7 +260,7 @@
 
   # AVB-sign the image as needed.
   if OPTIONS.info_dict.get("avb_enable") == "true":
-    avbtool = os.getenv('AVBTOOL') or OPTIONS.info_dict["avb_avbtool"]
+    avbtool = OPTIONS.info_dict["avb_avbtool"]
     part_size = OPTIONS.info_dict["dtbo_size"]
     # The AVB hash footer will be replaced if already present.
     cmd = [avbtool, "add_hash_footer", "--image", img.name,
@@ -428,7 +428,7 @@
     logger.info("%s.img already exists; not rebuilding...", name)
     return img.name
 
-  avbtool = os.getenv('AVBTOOL') or OPTIONS.info_dict["avb_avbtool"]
+  avbtool = OPTIONS.info_dict["avb_avbtool"]
   cmd = [avbtool, "make_vbmeta_image", "--output", img.name]
   common.AppendAVBSigningArgs(cmd, name)
 
diff --git a/tools/releasetools/build_image.py b/tools/releasetools/build_image.py
index 5e3d68a..bcbc921 100755
--- a/tools/releasetools/build_image.py
+++ b/tools/releasetools/build_image.py
@@ -739,6 +739,7 @@
   with open(filename, "w") as f:
     f.writelines(["%s=%s" % (key, value) for (key, value) in glob_dict.items()])
 
+
 def ExtractSystemOtherAvbKey(in_dir, glob_dict):
   if glob_dict.get("avb_system_extract_system_other_key") != "true":
     return
@@ -754,12 +755,13 @@
 
   # Extracts the public key used to sign system_other.img, into system.img:
   #   /system/etc/security/avb/system_other.avbpubkey.
-  avbtool = os.getenv('AVBTOOL') or glob_dict.get("avb_avbtool")
+  avbtool = glob_dict.get("avb_avbtool")
   extract_from = glob_dict.get("avb_system_other_key_path")
   cmd = [avbtool, "extract_public_key", "--key", extract_from,
          "--output", extract_to]
   common.RunAndCheckOutput(cmd, verbose=False)
 
+
 def main(argv):
   if len(argv) < 4 or len(argv) > 5:
     print(__doc__)
diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index e71667b..780b9c1 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -704,7 +704,7 @@
 
   # AVB: if enabled, calculate and add hash to boot.img or recovery.img.
   if info_dict.get("avb_enable") == "true":
-    avbtool = os.getenv('AVBTOOL') or info_dict["avb_avbtool"]
+    avbtool = info_dict["avb_avbtool"]
     part_size = info_dict[partition_name + "_size"]
     cmd = [avbtool, "add_hash_footer", "--image", img.name,
            "--partition_size", str(part_size), "--partition_name",