fix for issue with resolving bazel rc version (#262)

diff --git a/rules/version_check.bzl b/rules/version_check.bzl
index 2041b49..1ee6427 100644
--- a/rules/version_check.bzl
+++ b/rules/version_check.bzl
@@ -18,7 +18,7 @@
     return bazel_version
 
 def parse_rc(bazel_version):
-    if bazel_version.find("rc"):
+    if bazel_version.find("rc") != -1:
         rc = ""
         for i in range(len(bazel_version) - bazel_version.find("rc")):
             c = bazel_version[i]