Rollback a few recent Erlang changes to fix blame data

My combined patch for THRIFT-599 was committed, but it is preferable
commit the individual patches to preserve the more detailed log and
blame data.  I'll recommit r987018 as a sequence of patches and r988722
as its own rev.

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@990957 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/lib/erl/build/otp.mk b/lib/erl/build/otp.mk
index 0e0381e..1d16e2c 100644
--- a/lib/erl/build/otp.mk
+++ b/lib/erl/build/otp.mk
@@ -25,6 +25,7 @@
 
 # MHOST is the host where this Makefile runs.
 MHOST=${shell hostname -s}
+ERL_COMPILE_FLAGS+=-W0
 
 # The location of the erlang runtime system.
 ifndef ERL_RUN_TOP