Add a new x86(_64) arch variant "goldmont-without-xsaves"

Its target arch is goldmont, but without xsaves support.
This ensures efficient execution on a broad range of Intel/AMD CPUs used
in Chromebooks, including those lacking xsaves support.
(e.g. Kaby Lake, Gemini Lake, Alder Lake and AMD Zen series)

Bug: 314243939
Test: Build an image with TARGET_ARCH_VARIANT:=goldmont-without-xsaves
Change-Id: I9963cc3356394815f068fc998a9708bdb30c8266
diff --git a/rust/config/x86_device.go b/rust/config/x86_device.go
index 822f281..e7b575c 100644
--- a/rust/config/x86_device.go
+++ b/rust/config/x86_device.go
@@ -26,16 +26,17 @@
 	x86LinkFlags            = []string{}
 
 	x86ArchVariantRustFlags = map[string][]string{
-		"":              []string{},
-		"atom":          []string{"-C target-cpu=atom"},
-		"broadwell":     []string{"-C target-cpu=broadwell"},
-		"goldmont":      []string{"-C target-cpu=goldmont"},
-		"goldmont-plus": []string{"-C target-cpu=goldmont-plus"},
-		"haswell":       []string{"-C target-cpu=haswell"},
-		"ivybridge":     []string{"-C target-cpu=ivybridge"},
-		"sandybridge":   []string{"-C target-cpu=sandybridge"},
-		"silvermont":    []string{"-C target-cpu=silvermont"},
-		"skylake":       []string{"-C target-cpu=skylake"},
+		"":                        []string{},
+		"atom":                    []string{"-C target-cpu=atom"},
+		"broadwell":               []string{"-C target-cpu=broadwell"},
+		"goldmont":                []string{"-C target-cpu=goldmont"},
+		"goldmont-plus":           []string{"-C target-cpu=goldmont-plus"},
+		"goldmont-without-xsaves": []string{"-C target-cpu=goldmont", "-C target-feature=-xsaves"},
+		"haswell":                 []string{"-C target-cpu=haswell"},
+		"ivybridge":               []string{"-C target-cpu=ivybridge"},
+		"sandybridge":             []string{"-C target-cpu=sandybridge"},
+		"silvermont":              []string{"-C target-cpu=silvermont"},
+		"skylake":                 []string{"-C target-cpu=skylake"},
 		//TODO: Add target-cpu=stoneyridge when rustc supports it.
 		"stoneyridge": []string{""},
 		"tremont":     []string{"-C target-cpu=tremont"},