Run FD stress test in separate process (#35040)

As noted in #35011, the `stress` test is likely causing ENOMEM
errors in unrelated processes on FreeBSD as it's causing kernel
resource exhaustion. This fixes that by running that test with
a low FD ulimit (100). Should fix #23143. Closes #30511.

test/stress.jl

@@ -2,27 +2,9 @@
 
 # test for proper handling of FD exhaustion
 if Sys.isunix()
-    let ps = Pipe[]
-        ulimit_n = tryparse(Int, readchomp(`sh -c 'ulimit -n'`))
-        try
-            for i = 1:100*something(ulimit_n, 1000)
-                p = Pipe()
-                Base.link_pipe!(p)
-                push!(ps, p)
-            end
-            if ulimit_n === nothing
-                @warn "`ulimit -n` is set to unlimited, fd exhaustion cannot be tested"
-                @test_broken false
-            else
-                @test false
-            end
-        catch ex
-            isa(ex, Base.IOError) || rethrow()
-            @test ex.code in (Base.UV_EMFILE, Base.UV_ENFILE)
-        finally
-            foreach(close, ps)
-        end
-    end
+    # Run this test with a really small ulimit. If the ulimit is too high,
+    # we might saturate kernel resources (See #23143)
+    run(`sh -c "ulimit -n 100; $(Base.shell_escape(Base.julia_cmd())) --startup-file=no $(joinpath(@__DIR__, "stress_fd_exec.jl"))"`)
 end
 
 # issue 13559

test/stress_fd_exec.jl

@@ -0,0 +1,22 @@
+using Test
+let ps = Pipe[]
+    ulimit_n = tryparse(Int, readchomp(`sh -c 'ulimit -n'`))
+    try
+        for i = 1:100*something(ulimit_n, 1000)
+            p = Pipe()
+            Base.link_pipe!(p)
+            push!(ps, p)
+        end
+        if ulimit_n === nothing
+            @warn "`ulimit -n` is set to unlimited, fd exhaustion cannot be tested"
+            @test_broken false
+        else
+            @test false
+        end
+    catch ex
+        isa(ex, Base.IOError) || rethrow()
+        @test ex.code in (Base.UV_EMFILE, Base.UV_ENFILE)
+    finally
+        foreach(close, ps)
+    end
+end