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/llvm-context/src/polkavm/context/argument.rs

@@ -66,9 +66,9 @@ impl<'ctx> Argument<'ctx> {
     /// Access the underlying value.
     ///
     /// Will emit a stack load if `self` is a pointer argument.
-    pub fn access<D: crate::polkavm::Dependency + Clone>(
+    pub fn access(
         &self,
-        context: &crate::polkavm::context::Context<'ctx, D>,
+        context: &crate::polkavm::context::Context<'ctx>,
     ) -> anyhow::Result<inkwell::values::BasicValueEnum<'ctx>> {
         match &self.value {
             Value::Register(value) => Ok(*value),
@@ -79,9 +79,9 @@ impl<'ctx> Argument<'ctx> {
     /// Access the underlying value.
     ///
     /// Will emit a stack load if `self` is a pointer argument.
-    pub fn as_pointer<D: crate::polkavm::Dependency + Clone>(
+    pub fn as_pointer(
         &self,
-        context: &crate::polkavm::context::Context<'ctx, D>,
+        context: &crate::polkavm::context::Context<'ctx>,
     ) -> anyhow::Result<crate::polkavm::context::Pointer<'ctx>> {
         match &self.value {
             Value::Register(value) => {