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/integration/src/cases.rs

@@ -12,6 +12,26 @@ pub struct Contract {
     pub calldata: Vec<u8>,
 }
 
+impl Contract {
+    pub fn build(calldata: Vec<u8>, name: &'static str, code: &str) -> Self {
+        Self {
+            name,
+            evm_runtime: compile_evm_bin_runtime(name, code),
+            pvm_runtime: compile_blob(name, code),
+            calldata,
+        }
+    }
+
+    pub fn build_size_opt(calldata: Vec<u8>, name: &'static str, code: &str) -> Self {
+        Self {
+            name,
+            evm_runtime: compile_evm_bin_runtime(name, code),
+            pvm_runtime: compile_blob_with_options(name, code, true, OptimizerSettings::size()),
+            calldata,
+        }
+    }
+}
+
 macro_rules! case {
     // Arguments:
     //     1. The file name, expect to live under "../contracts/"
@@ -261,26 +281,6 @@ sol!(
 case!("AddressPredictor.sol", Predicted, constructorCall, predicted_constructor, salt: U256);
 case!("AddressPredictor.sol", AddressPredictor, constructorCall, address_predictor_constructor, salt: U256, bytecode: Bytes);
 
-impl Contract {
-    pub fn build(calldata: Vec<u8>, name: &'static str, code: &str) -> Self {
-        Self {
-            name,
-            evm_runtime: compile_evm_bin_runtime(name, code),
-            pvm_runtime: compile_blob(name, code),
-            calldata,
-        }
-    }
-
-    pub fn build_size_opt(calldata: Vec<u8>, name: &'static str, code: &str) -> Self {
-        Self {
-            name,
-            evm_runtime: compile_evm_bin_runtime(name, code),
-            pvm_runtime: compile_blob_with_options(name, code, true, OptimizerSettings::size()),
-            calldata,
-        }
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use rayon::iter::{IntoParallelIterator, ParallelIterator};