package/cpp-httplib: link with libatomic if needed

Buildroot commit 8dad17ea06 bumped the
package from 0.27.0 to 0.37.2. This bump includes upstream commit
464867a9ce
which added WebSocket support to version 0.33.0 and causes a build error
detected by the Gitlab pipelines for bootlin-sparc-uclibc:

/builds/bkuhls/buildroot/br-test-pkg/bootlin-sparc-uclibc/host/opt/ext-toolchain/bin/../lib/gcc/sparc-buildroot-linux-uclibc/14.3.0/../../../../sparc-buildroot-linux-uclibc/bin/ld:
 /tmp/cciyXsAR.ltrans6.ltrans.o: in function
 `httplib::ws::WebSocket::close(httplib::ws::CloseStatus,
 std::__cxx11::basic_string<char, std::char_traits<char>,
 std::allocator<char> > const&)':
<artificial>:(.text+0x6408): undefined reference to `__atomic_exchange_1'

To fix the problem we add -latomic to LDFLAGS when needed.

Signed-off-by: Bernd Kuhls <bernd@kuhls.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/cpp-httplib/Config.in

@@ -1,9 +1,11 @@
 comment "cpp-httplib needs a toolchain w/ C++, wchar, threads"
+	depends on BR2_TOOLCHAIN_HAS_ATOMIC
 	depends on !BR2_INSTALL_LIBSTDCPP || !BR2_USE_WCHAR || !BR2_TOOLCHAIN_HAS_THREADS
 
 config BR2_PACKAGE_CPP_HTTPLIB
 	bool "cpp-httplib"
 	depends on BR2_INSTALL_LIBSTDCPP
+	depends on BR2_TOOLCHAIN_HAS_ATOMIC
 	depends on BR2_TOOLCHAIN_HAS_THREADS
 	depends on BR2_USE_WCHAR
 	help

package/cpp-httplib/cpp-httplib.mk

@@ -13,6 +13,12 @@ CPP_HTTPLIB_INSTALL_STAGING = YES
 CPP_HTTPLIB_CONF_OPTS = \
 	-Dtest=false
 
+CPP_HTTPLIB_LDFLAGS = $(TARGET_LDFLAGS)
+
+ifeq ($(BR2_TOOLCHAIN_HAS_LIBATOMIC),y)
+CPP_HTTPLIB_LDFLAGS += -latomic
+endif
+
 ifeq ($(BR2_PACKAGE_CPP_HTTPLIB_COMPILE),y)
 CPP_HTTPLIB_CONF_OPTS += -Dcompile=true
 CPP_HTTPLIB_DEPENDENCIES += host-python3