Add libm linkage to toolchains

PiperOrigin-RevId: 513350744

toolchain/cc_toolchain_config.bzl

diff --git a/toolchain/cc_toolchain_config.bzl b/toolchain/cc_toolchain_config.bzl
index b610a8e..3bfe1bf 100644
--- a/toolchain/cc_toolchain_config.bzl
+++ b/toolchain/cc_toolchain_config.bzl
@@ -98,6 +98,7 @@
                         flags = [
                             "-B" + ctx.attr.linker_path,
                             "-lstdc++",
+                            "-lm",
                             "--target=" + ctx.attr.target_full_name,
                         ] + ctx.attr.extra_linker_flags,
                     ),