Fix CI AArch64 Linux musl builds

This is required to get PR #640 and further work on the repository
moving.

.cargo/config.toml

@@ -1,9 +1,19 @@
-# Remove this if targeting AArch64 from an AArch64 Linux box
+# May need to remove these if targeting AArch64 from an AArch64 Linux box
+
 [target.'cfg(all(target_os = "linux", target_arch = "aarch64"))']
-runner = 'qemu-aarch64'
+runner = "qemu-aarch64"
 
 [target.aarch64-unknown-linux-gnu]
-linker = 'aarch64-linux-gnu-gcc'
+linker = "aarch64-linux-gnu-gcc"
 
 [target.aarch64-unknown-linux-musl]
-linker = 'aarch64-linux-musl-gcc'
+linker = "aarch64-linux-musl-gcc"
+# AArch64 Linux musl targets are repeatedly affected under varying
+# circumstances by fixedn't linking issues to compiler builtin symbols.
+# Linking to libgcc, though arguably an inelegant hack that's only portable
+# to our glibc from musl crosscompilation scenario, is effective to reliably
+# provide an implementation of those fundamental symbols over time, without
+# user-visible impacts on the final executables. See:
+# https://github.com/rust-lang/rust/issues/46651
+# https://github.com/rust-lang/compiler-builtins/issues/201
+rustflags = ["-Clink-args=-lgcc"]