use host defaults for can_run target triple

src/dist/dist.rs

@@ -322,11 +322,25 @@ impl TargetTriple {
         // Otherwise we need to parse things
         let partial_self = PartialTargetTriple::new(&self.0)
             .ok_or_else(|| anyhow!(format!("Unable to parse target triple: {}", self.0)))?;
-        let partial_other = PartialTargetTriple::new(&other.0)
+        let mut partial_other = PartialTargetTriple::new(&other.0)
             .ok_or_else(|| anyhow!(format!("Unable to parse target triple: {}", other.0)))?;
-        // First obvious check is OS, if that doesn't match then we know it
-        // can't run unless an OS isn't specified
-        let ret = if partial_self.os != partial_other.os && partial_other.os.is_some() {
+
+        // Default to host for missing target triple values
+        if partial_other.arch.is_none() {
+            partial_other.arch = partial_self.clone().arch;
+        }
+        if partial_other.os.is_none() {
+            partial_other.os = partial_self.clone().os;
+        }
+        if partial_other.env.is_none() {
+            partial_other.env = partial_self.clone().env;
+        }
+
+        // Check if the other triple with host defaults applied matches
+        let ret = if partial_self == partial_other {
+            true
+        } else if partial_self.os != partial_other.os {
+            // Then check OS, if that doesn't match there's no chance
             false
         } else if partial_self.os.as_deref() == Some("pc-windows") {
             // Windows is a special case here, we know we can run 32bit on 64bit
@@ -336,8 +350,8 @@ impl TargetTriple {
                 || (partial_self.arch.as_deref() == Some("x86_64")
                     && partial_other.arch.as_deref() == Some("i686"))
         } else {
-            // For other OSes, for now, we assume other toolchains won't run if an OS is specified
-            partial_other.os.is_none()
+            // For other OSes, for now, we assume other toolchains won't run
+            false
         };
         Ok(ret)
     }