Add CAIRO_DEBUG_SIERRA_GEN env var..

Author: ilyalesokhin-starkware

crates/cairo-lang-compiler/src/db.rs

@@ -46,8 +46,17 @@ impl ExternalCodeSizeEstimator for RootDatabase {
                     // probably too large for inline so we can just return the max size.
                     return Ok(isize::MAX);
                 }
+                if std::env::var("CAIRO_DEBUG_SIERRA_GEN").is_ok() {
+                    // If we are debugging sierra generation, we want to finish the compilation
+                    // rather than panic.
+                    return Ok(isize::MAX);
+                }
 
-                panic!("Failed to compile program to casm.");
+                panic!(
+                    "Internal compiler error: Failed to compile program to casm. You can set the \
+                     CAIRO_DEBUG_SIERRA_GEN environment if you want to finish the compilation and \
+                     debug the sierra program."
+                );
             }
         };
         let casm = builder.casm_program();