[ELF,test] Add env LLD_IN_TEST=1 to make some tests work if RUN_LLD_MAIN_TWICE

Author: MaskRay

lld/test/ELF/basic.s

@@ -220,7 +220,7 @@ _start:
 
 ## Test erroring on a recursive response file, but only once.
 # RUN: echo @%t.responsefile > %t.responsefile
-# RUN: not ld.lld %t @%t.responsefile 2>&1 | FileCheck %s --check-prefix=RECRSP
+# RUN: env LLD_IN_TEST=1 not ld.lld %t @%t.responsefile 2>&1 | FileCheck %s --check-prefix=RECRSP
 # RECRSP: recursive expansion of: '{{.*}}.responsefile'
 # RECRSP-NOT: recursive expansion of
 

lld/test/ELF/stdout.s

@@ -2,7 +2,7 @@
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
 ## Test that we only write to "-" once.
-# RUN: LLD_IN_TEST=2 ld.lld %t.o -o - > %t1
+# RUN: env LLD_IN_TEST=2 ld.lld %t.o -o - > %t1
 # RUN: llvm-objdump -d %t1 | FileCheck %s
 
 # CHECK: nop