Separate compilation and linker phases (#376)

Separate between compilation and linker phases to allow deploy time
linking and back-porting era compiler changes to fix #91. Unlinked
contract binaries (caused by missing libraries or missing factory
dependencies in turn) are emitted as raw ELF object.

Few drive by fixes:
- #98
- A compiler panic on missing libraries definitions.
- Fixes some incosistent type forwarding in JSON output (empty string
vs. null object).
- Remove the unused fallback for size optimization setting.
- Remove the broken `--lvm-ir`  mode.
- CI workflow fixes.

---------

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>
Signed-off-by: xermicus <bigcyrill@hotmail.com>
Signed-off-by: xermicus <cyrill@parity.io>

crates/common/src/metadata.rs

@@ -0,0 +1,42 @@
+//! The metadata hash type.
+
+use std::str::FromStr;
+
+use serde::{Deserialize, Serialize};
+
+/// The metadata hash type.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
+pub enum MetadataHash {
+    /// Do not include bytecode hash.
+    #[serde(rename = "none")]
+    None,
+    /// Include the `ipfs` hash.
+    #[serde(rename = "ipfs")]
+    IPFS,
+    /// Include the `keccak256`` hash.
+    #[serde(rename = "keccak256")]
+    Keccak256,
+}
+
+impl FromStr for MetadataHash {
+    type Err = anyhow::Error;
+
+    fn from_str(string: &str) -> Result<Self, Self::Err> {
+        match string {
+            "none" => Ok(Self::None),
+            "ipfs" => Ok(Self::IPFS),
+            "keccak256" => Ok(Self::Keccak256),
+            string => anyhow::bail!("unknown bytecode hash mode: `{string}`"),
+        }
+    }
+}
+
+impl std::fmt::Display for MetadataHash {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        match self {
+            Self::None => write!(f, "none"),
+            Self::IPFS => write!(f, "ipfs"),
+            Self::Keccak256 => write!(f, "keccak256"),
+        }
+    }
+}