llvm-context: alloca at the function entry if possible (#283)

Closes  #48

Change the code size test to no longer emit debug info as to get a more
accurate picture.

---------

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

crates/llvm-context/src/polkavm/const/mod.rs

@@ -9,6 +9,9 @@ pub static XLEN: usize = revive_common::BIT_LENGTH_X32;
 /// The calldata size global variable name.
 pub static GLOBAL_CALLDATA_SIZE: &str = "calldatasize";
 
+/// The spill buffer global variable name.
+pub static GLOBAL_ADDRESS_SPILL_BUFFER: &str = "address_spill_buffer";
+
 /// The deployer call header size that consists of:
 /// - bytecode hash (32 bytes)
 pub const DEPLOYER_CALL_HEADER_SIZE: usize = revive_common::BYTE_LENGTH_WORD;