[gcc(refs/vendors/ARM/heads/arm-struct-reorg-wip)] syscall: append to environment in tests, don't clobber it

[Tamar Christina]

https://gcc.gnu.org/g:fbfa806e65c552e81b363756fd8e2925651f7333

commit fbfa806e65c552e81b363756fd8e2925651f7333
Author: Ian Lance Taylor <iant@golang.org>
Date:   Mon May 11 16:23:44 2020 -0700

    syscall: append to environment in tests, don't clobber it
    
    This is a partial backport of https://golang.org/cl/233318.
    It's only a partial backport because part of the change was
    already applied to libgo in CL 193497 as part of the update
    to the Go 1.13beta1 release.
    
    Fixes PR go/95061
    
    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/233359

Diff:
---
 libgo/go/syscall/syscall_linux_test.go | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/libgo/go/syscall/syscall_linux_test.go b/libgo/go/syscall/syscall_linux_test.go
index 97059c87d3d..c12df4cf5c7 100644
--- a/libgo/go/syscall/syscall_linux_test.go
+++ b/libgo/go/syscall/syscall_linux_test.go
@@ -187,7 +187,7 @@ func TestLinuxDeathSignal(t *testing.T) {
 	}
 
 	cmd := exec.Command(tmpBinary)
-	cmd.Env = []string{"GO_DEATHSIG_PARENT=1"}
+	cmd.Env = append(os.Environ(), "GO_DEATHSIG_PARENT=1")
 	chldStdin, err := cmd.StdinPipe()
 	if err != nil {
 		t.Fatalf("failed to create new stdin pipe: %v", err)
@@ -225,7 +225,10 @@ func TestLinuxDeathSignal(t *testing.T) {
 
 func deathSignalParent() {
 	cmd := exec.Command(os.Args[0])
-	cmd.Env = []string{"GO_DEATHSIG_CHILD=1"}
+	cmd.Env = append(os.Environ(),
+		"GO_DEATHSIG_PARENT=",
+		"GO_DEATHSIG_CHILD=1",
+	)
 	cmd.Stdin = os.Stdin
 	cmd.Stdout = os.Stdout
 	attrs := syscall.SysProcAttr{
@@ -360,7 +363,7 @@ func TestSyscallNoError(t *testing.T) {
 	}
 
 	cmd := exec.Command(tmpBinary)
-	cmd.Env = []string{"GO_SYSCALL_NOERROR=1"}
+	cmd.Env = append(os.Environ(), "GO_SYSCALL_NOERROR=1")
 
 	out, err := cmd.CombinedOutput()
 	if err != nil {