Fix warnings in build config files (#2258)

Author: jordwalke

src/reason-parser/vendor/cmdliner/dune

@@ -0,0 +1,5 @@
+(library
+ (name ReasonCmdliner)
+ (public_name reason.cmdliner)
+  (wrapped false)
+  (flags :standard -w -3-27-32-35-50))

src/reason-parser/vendor/cmdliner/jbuild

@@ -0,0 +1,5 @@
+(library
+ (name ReasonEasyFormat)
+ (public_name reason.easy_format)
+  (wrapped false)
+  (flags (:standard -w -9-27)))

src/reason-parser/vendor/easy_format/dune

@@ -8,7 +8,7 @@
  (public_name rtop)
  (modules reason_util reason_utop reason_toploop)
  (wrapped false)
- (libraries menhirLib reason.easy_format reason utop ocaml-migrate-parsetree))
+ (libraries compiler-libs.common menhirLib reason.easy_format reason utop ocaml-migrate-parsetree))
 
 (executable
  (name rtop)