clang'ed buildworld is failing with -O0

Hi,

I've recently tried to buildworld with clang using DEBUG_FLAGS=-g -O0
(as clang(1) specifies that -g is most useful with -O0).

Short version:
clang -O2 -pipe -I. -I/data/src/freebsd/base/head/usr.bin/xlint/lint1
-I/data/src/freebsd/base/head/usr.bin/xlint/lint1/../arch/amd64
-I/data/src/freebsd/base/head/usr.bin/xlint/lint1/../common -g -O0
-std=gnu99
-I/usr/obj/data/src/freebsd/base/head/tmp/legacy/usr/include  -static
-L/usr/obj/data/src/freebsd/base/head/tmp/legacy/usr/lib -o lint1
cgram.o scan.o mem1.o mem.o err.o main1.o decl.o tree.o func.o init.o
emit.o emit1.o inittyp.o -ll -lm -legacy
clang: warning: argument unused during compilation: '-g'
clang: warning: argument unused during compilation: '-std=gnu99'
/usr/lib/libc.a(isnan.o): In function `__isnanf':
/data/src/freebsd/base/head/lib/libc/gen/isnan.c:52: multiple definition
of `__isnanf'
/usr/lib/libm.a(s_isnan.o):/data/src/freebsd/base/head/lib/msun/src/s_isnan.c:47:
first defined here
clang: error: linker command failed with exit code 1 (use -v to see
invocation)

Full build log (if it's useful, ~5MB):
http://darklight.org.ru/misc/buildworld-clang-O0.txt

Any hints on what I'm doing wrong?


TIA,
Yuri