[ELF][test] Add a test about GCable SHF_LINK_ORDER SHT_INIT_ARRAY

Author: MaskRay

lld/test/ELF/gc-sections-linkorder.s

@@ -5,6 +5,7 @@
 
 # CHECK: removing unused section {{.*}}.o:(.foo2)
 # CHECK: removing unused section {{.*}}.o:(bar2)
+# CHECK: removing unused section {{.*}}.o:(.init_array.bar2)
 # CHECK: removing unused section {{.*}}.o:(.zed2)
 
 .global _start
@@ -25,6 +26,11 @@ _start:
 .quad .zed2
 .quad .foo2
 
+## An SHT_INIT_ARRAY with the SHF_LINK_ORDER flag can be GCed.
+.section .init_array.bar2,"awo",@init_array,.foo2
+.quad .zed2
+.quad .foo2
+
 .section .zed1,"a"
 .quad 0