cmd/compile/internal/test: make TestIntendedInlining faster

There is no need to build with -a. The go command should do the
right thing to pass the flags. Also, we only care packages
mentioned on the command line, so no need to add -gcflags=all=....

May fix #52081.

Change-Id: Idabcfe285c90ed5d25ea6d42abd7617078d3283a
Reviewed-on: https://go-review.googlesource.com/c/go/+/407015
Reviewed-by: Keith Randall <khr@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Keith Randall <khr@golang.org>

src/cmd/compile/internal/test/inl_test.go

diff --git a/src/cmd/compile/internal/test/inl_test.go b/src/cmd/compile/internal/test/inl_test.go
index 3fd45f2..49ee88e 100644
--- a/src/cmd/compile/internal/test/inl_test.go
+++ b/src/cmd/compile/internal/test/inl_test.go
@@ -275,7 +275,7 @@
 		}
 	}
 
-	args := append([]string{"build", "-a", "-gcflags=all=-m -m", "-tags=math_big_pure_go"}, pkgs...)
+	args := append([]string{"build", "-gcflags=-m -m", "-tags=math_big_pure_go"}, pkgs...)
 	cmd := testenv.CleanCmdEnv(exec.Command(testenv.GoToolPath(t), args...))
 	pr, pw := io.Pipe()
 	cmd.Stdout = pw