Link -lregex on QNX

According to the 2nd point on [1], -lregex is required on QNX.

[1] https://www.qnx.com/developers/docs/7.1/#com.qnx.doc.ide.userguide/topic/writing_test_programs.html

BUILD.bazel

@@ -110,7 +110,7 @@ cc_library(
         "googletest/include",
     ],
     linkopts = select({
-        ":qnx": [],
+        ":qnx": ["-lregex"],
         ":windows": [],
         "//conditions:default": ["-pthread"],
     }),