Makefile: Unexport LC_ALL instead of clearing it

Apparently not all versions of glibc and utilities treat an empty
LC_ALL as nonexistent, causing error messages to be garbled.  Instead,
explicitly unexport it from the environment.
Reported-and-tested-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
LKML-Reference: <4B2AC394.4030108@redhat.com>
Cc: Michal Marek <mmarek@sues.cz>
Cc: Roland Dreier <rdreier@cisco.com>
Cc: Sam Ravnborg <sam@ravnborg.org>

Makefile

@@ -17,11 +17,11 @@ NAME = Man-Eating Seals of Antiquity
 MAKEFLAGS += -rR --no-print-directory
 
 # Avoid funny character set dependencies
-LC_ALL=
+unexport LC_ALL
 LC_CTYPE=C
 LC_COLLATE=C
 LC_NUMERIC=C
-export LC_ALL LC_CTYPE LC_COLLATE LC_NUMERIC
+export LC_CTYPE LC_COLLATE LC_NUMERIC
 
 # We are using a recursive build, so we need to do a little thinking
 # to get the ordering right.