Disable thread affinity test under rr

RR changes the affinity, so 0,1 may not be available in the affinity
mask. It's a bit complicated to fix this test and would require parsing
the existing affinity mask, so just disable it for now.

test/threads.jl

@@ -11,10 +11,17 @@ let cmd = `$(Base.julia_cmd()) --depwarn=error --startup-file=no threads_exec.jl
 end
 
 # issue #34415 - make sure external affinity settings work
-if Sys.islinux() && Sys.CPU_THREADS > 1 && Sys.which("taskset") !== nothing
-    run_with_affinity(spec) = readchomp(`taskset -c $spec $(Base.julia_cmd()) -e "run(\`taskset -p \$(getpid())\`)"`)
-    @test endswith(run_with_affinity("1"), "2")
-    @test endswith(run_with_affinity("0,1"), "3")
+
+if Sys.islinux()
+    const SYS_rrcall_check_presence = 1008
+    running_under_rr() = 0 == ccall(:syscall, Int,
+        (Int, Int, Int, Int, Int, Int, Int),
+        SYS_rrcall_check_presence, 0, 0, 0, 0, 0, 0)
+    if Sys.CPU_THREADS > 1 && Sys.which("taskset") !== nothing && !running_under_rr()
+        run_with_affinity(spec) = readchomp(`taskset -c $spec $(Base.julia_cmd()) -e "run(\`taskset -p \$(getpid())\`)"`)
+        @test endswith(run_with_affinity("1"), "2")
+        @test endswith(run_with_affinity("0,1"), "3")
+    end
 end
 
 # issue #34769