tests: mark backtrace test case as broken on FreeBSD (JuliaLang#22508)

See also: JuliaLang#22472

test/cmdlineargs.jl

@@ -423,7 +423,12 @@ end
 for precomp in ("yes", "no")
     bt = readstring(pipeline(ignorestatus(`$(Base.julia_cmd()) --startup-file=no --precompiled=$precomp
         -E 'include("____nonexistent_file")'`), stderr=catcmd))
-    @test contains(bt, "include_from_node1(::Module, ::String) at $(joinpath(".", "loading.jl"))")
+    if (is_bsd() && !is_apple()) && precomp == "yes"
+        # FIXME: #20798 (FreeBSD)
+        @test_broken contains(bt, "include_from_node1(::Module, ::String) at $(joinpath(".", "loading.jl"))")
+    else
+        @test contains(bt, "include_from_node1(::Module, ::String) at $(joinpath(".", "loading.jl"))")
+    end
     lno = match(r"at \.[\/\\]loading\.jl:(\d+)", bt)
     @test length(lno.captures) == 1
     @test parse(Int, lno.captures[1]) > 0