Got basic code building with the roboRIO compiler.

Change-Id: I158caa4786542344e91949c62fd95a79015b653b
diff --git a/third_party/libevent/BUILD b/third_party/libevent/BUILD
index 50f714a..b576f52 100644
--- a/third_party/libevent/BUILD
+++ b/third_party/libevent/BUILD
@@ -1,5 +1,7 @@
 licenses(['notice'])
 
+load('/tools/build_rules/select', 'compiler_select')
+
 cc_library(
   name = 'libevent',
   visibility = ['//visibility:public'],
@@ -56,7 +58,9 @@
     '-Wno-unused-parameter',
     '-Wno-format-nonliteral',
     '-Wno-cast-qual',
-    '-Wno-incompatible-pointer-types-discards-qualifiers',
     '-Wno-unused-function',
-  ],
+  ] + compiler_select({
+      'gcc': [],
+      'clang': ['-Wno-incompatible-pointer-types-discards-qualifiers']
+  }),
 )
diff --git a/third_party/libevent/buffer.c b/third_party/libevent/buffer.c
index 80a9e1b..de4ab52 100644
--- a/third_party/libevent/buffer.c
+++ b/third_party/libevent/buffer.c
@@ -2749,7 +2749,7 @@
 	if (!chain)
 		return (-1);
 	chain->flags |= EVBUFFER_REFERENCE | EVBUFFER_IMMUTABLE;
-	chain->buffer = (const u_char *)data;
+	chain->buffer = (u_char *)data;
 	chain->buffer_len = datlen;
 	chain->off = datlen;