gcc trunk and -lmpc

[Alexey Salmin]

Hello! Today I tried to build latest gcc trunk (rev #158628) and got
the following errors:

libbackend.a(builtins.o): In function `fold_builtin_ccos':
/home/salmin/gcc-trunk/host-x86_64-unknown-linux-gnu/gcc/../.././gcc/builtins.c:7341:
undefined reference to `mpc_cosh'
/home/salmin/gcc-trunk/host-x86_64-unknown-linux-gnu/gcc/../.././gcc/builtins.c:7341:
undefined reference to `mpc_cos'
libbackend.a(builtins.o): In function `fold_builtin_cexp':
/home/salmin/gcc-trunk/host-x86_64-unknown-linux-gnu/gcc/../.././gcc/builtins.c:7434:
undefined reference to `mpc_exp'
....

which is surprising because I have libmpc installed (debian sid):
salmin@salmin:~/gcc-trunk$ dpkg -l libmpc* | grep ^ii | grep -v libmpcdec
ii  libmpc-dev                           0.8.1-1
         multiple precision complex floating-point library development
package
ii  libmpc2                              0.8.1-1
         multiple precision complex floating-point library

configuring with LDFLAGS=-lmpc solved the problem. Is it a bug in
Makefile or something or I'm doing it wrong?

Alexey