build: Forbid linking glibc statically again

Static linking against glibc has crashes depending on the name
resolution setup (I think when it needs to dlopen). It is a fundamental glibc
limitation that we cannot fix on our end.

It will crash when doing `echo ~<TAB>`.

This carves out a specific exception for "gnu", i.e. glibc, targets.

Other targets, including musl and other operating systems, continue to
allow static linking.

build.rs

@@ -50,6 +50,9 @@ fn main() {
     // Keep verbose mode on until we've ironed out rust build script stuff
     target.set_verbose(true);
     detect_cfgs(&mut target);
+
+    #[cfg(all(target_env = "gnu", target_feature = "crt-static"))]
+    compile_error!("Statically linking against glibc has unavoidable crashes and is unsupported. Use dynamic linking or link statically against musl.");
 }
 
 /// Check target system support for certain functionality dynamically when the build is invoked,