build: more mingw fixes

More mingw build failures:

  CCLD     libvirt-lxc.la
/usr/lib64/gcc/i686-w64-mingw32/4.7.2/../../../../i686-w64-mingw32/bin/ld: cannot find libvirt_lxc.def: No such file or directory

  CC       virportallocatortest-virportallocatortest.o
../../tests/virportallocatortest.c: In function 'main':
../../tests/virportallocatortest.c:195:1: error: implicit declaration of function 'setenv' [-Werror=implicit-function-declaration]

* src/Makefile.am (GENERATED_SYM_FILES): Also generate
libvirt_lxc.def.
* bootstrap.conf (gnulib_modules): Import setenv.

bootstrap.conf

@@ -92,6 +92,7 @@ regex
 random_r
 sched
 send
+setenv
 setsockopt
 sigaction
 sigpipe

src/Makefile.am

@@ -1462,7 +1462,8 @@ EXTRA_DIST += \
   libvirt_xenxs.syms	\
   libvirt_libssh2.syms
 
-GENERATED_SYM_FILES = libvirt.syms libvirt.def libvirt_qemu.def
+GENERATED_SYM_FILES = \
+	libvirt.syms libvirt.def libvirt_qemu.def libvirt_lxc.def
 
 BUILT_SOURCES += $(GENERATED_SYM_FILES)