Extract target triple and linking logic

compiler/build/src/link.rs

@@ -0,0 +1,66 @@
+use crate::target::arch_str;
+use std::io;
+use std::path::Path;
+use std::process::{Child, Command};
+use target_lexicon::{Architecture, OperatingSystem, Triple};
+
+pub fn link(
+    target: &Triple,
+    binary_path: &Path,
+    host_input_path: &Path,
+    dest_filename: &Path,
+) -> io::Result<Child> {
+    match target {
+        Triple {
+            architecture: Architecture::X86_64,
+            operating_system: OperatingSystem::Linux,
+            ..
+        } => link_linux(
+            arch_str(target),
+            binary_path,
+            host_input_path,
+            dest_filename,
+        ),
+        Triple {
+            architecture: Architecture::X86_64,
+            operating_system: OperatingSystem::Darwin,
+            ..
+        } => todo!("link macos"),
+        _ => panic!("TODO gracefully handle unsupported target: {:?}", target),
+    }
+}
+
+fn link_linux(
+    arch: &str,
+    binary_path: &Path,
+    host_input_path: &Path,
+    dest_filename: &Path,
+) -> io::Result<Child> {
+    Command::new("ld")
+        .args(&[
+            "-arch",
+            arch,
+            "/usr/lib/x86_64-linux-gnu/crti.o",
+            "/usr/lib/x86_64-linux-gnu/crtn.o",
+            "/usr/lib/x86_64-linux-gnu/Scrt1.o",
+            "-dynamic-linker",
+            "/lib64/ld-linux-x86-64.so.2",
+            // Libraries - see https://github.com/rtfeldman/roc/pull/554#discussion_r496365925
+            // for discussion and further references
+            "-lc",
+            "-lm",
+            "-lpthread",
+            "-ldl",
+            "-lrt",
+            "-lutil",
+            "-lc_nonshared",
+            // "-lc++", // TODO shouldn't we need this?
+            // "-lgcc", // TODO will eventually need compiler_rt from gcc or something - see https://github.com/rtfeldman/roc/pull/554#discussion_r496370840
+            // "-lunwind", // TODO will eventually need this, see https://github.com/rtfeldman/roc/pull/554#discussion_r496370840
+            "-o",
+            binary_path.to_str().unwrap(),     // app
+            host_input_path.to_str().unwrap(), // host.o
+            dest_filename.to_str().unwrap(),   // roc_app.o
+        ])
+        .spawn()
+}