package/mutt: link with -latomic if needed

Link with -latomic if needed to avoid the following build failure with
openssl:

configure:10549: checking for X509_STORE_CTX_new in -lcrypto
configure:10574: /tmp/instance-0/output-1/host/bin/sparc-linux-gcc -o conftest -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64  -Os -g0  -static -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -I/tmp/instance-0/output-1/host/sparc-buildroot-linux-uclibc/sysroot/usr/include  -static -L/tmp/instance-0/output-1/host/sparc-buildroot-linux-uclibc/sysroot/usr/lib conftest.c -lcrypto -lz  >&5
/tmp/instance-0/output-1/host/opt/ext-toolchain/bin/../lib/gcc/sparc-buildroot-linux-uclibc/9.3.0/../../../../sparc-buildroot-linux-uclibc/bin/ld: /tmp/instance-0/output-1/host/sparc-buildroot-linux-uclibc/sysroot/usr/lib/libcrypto.a(x509cset.o): in function `X509_CRL_up_ref':
x509cset.c:(.text+0xfc): undefined reference to `__atomic_fetch_add_4'

Ideally, mutt should use pkg-config but upstream don't want to use it:
https://gitlab.com/muttmua/mutt/-/merge_requests/25

Fixes:
 - http://autobuild.buildroot.org/results/e357984853f8ca879156245717fadbeaa9b0dbae

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/mutt/mutt.mk

@@ -12,6 +12,10 @@ MUTT_CPE_ID_VENDOR = mutt
 MUTT_DEPENDENCIES = ncurses
 MUTT_CONF_OPTS = --disable-doc --disable-smtp
 
+ifeq ($(BR2_TOOLCHAIN_HAS_LIBATOMIC),y)
+MUTT_CONF_ENV += LIBS=-latomic
+endif
+
 ifeq ($(BR2_PACKAGE_LIBICONV),y)
 MUTT_DEPENDENCIES += libiconv
 MUTT_CONF_OPTS += --enable-iconv