sh: Fix some bugs with backquoted builtins:

- correctly handle error output in $(builtin 2>&1), clarify out1/out2 vs
  output/errout in the code
- treat all builtins as regular builtins so errors do not abort the shell
  and variable assignments do not persist
- respect the caller's INTOFF

Some bugs still exist:
- expansion errors may still abort the shell
- some side effects of expansions and builtins persist

1 files changed, 2 insertions, 2 deletions

diff --git a/bin/sh/error.c b/bin/sh/error.c
index 3fc7101..1f981f0 100644
--- a/bin/sh/error.c
+++ b/bin/sh/error.c
@@ -160,8 +160,8 @@ exverror(int cond, const char *msg, va_list ap)
 #endif
 	if (msg) {
 		if (commandname)
-			outfmt(&errout, "%s: ", commandname);
-		doformat(&errout, msg, ap);
+			outfmt(out2, "%s: ", commandname);
+		doformat(out2, msg, ap);
 		out2c('\n');
 	}
 	flushall();