Add QNX and OSX to known platforms (#1853)

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**What type of PR is this?**

> Uncomment one line below and remove others.
>
Bug fix

**What package or component does this PR mostly affect?**

language/go
cmd/gazelle

**What does this PR do? Why is it needed?**

Adding more known platforms to avoid issue reported in
#1735.

**Which issues(s) does this PR fix?**

Fixes #1735

**Other notes for review**

language/go/testdata/cgolib_with_build_tags/BUILD.want

@@ -49,9 +49,15 @@ go_library(
         "@io_bazel_rules_go//go/platform:openbsd": [
             "example.com/repo/lib/deep",
         ],
+        "@io_bazel_rules_go//go/platform:osx": [
+            "example.com/repo/lib/deep",
+        ],
         "@io_bazel_rules_go//go/platform:plan9": [
             "example.com/repo/lib/deep",
         ],
+        "@io_bazel_rules_go//go/platform:qnx": [
+            "example.com/repo/lib/deep",
+        ],
         "@io_bazel_rules_go//go/platform:solaris": [
             "example.com/repo/lib/deep",
         ],

rule/platform.go

@@ -87,6 +87,14 @@ var KnownPlatforms = []Platform{
 	{"openbsd", "amd64"},
 	{"openbsd", "arm"},
 	{"openbsd", "arm64"},
+	{"osx", "386"},
+	{"osx", "amd64"},
+	{"osx", "arm"},
+	{"osx", "arm64"},
+	{"qnx", "386"},
+	{"qnx", "amd64"},
+	{"qnx", "arm"},
+	{"qnx", "arm64"},
 	{"plan9", "386"},
 	{"plan9", "amd64"},
 	{"plan9", "arm"},