feat(forge build): err if no source file in specified paths

crates/forge/bin/cmd/build.rs

@@ -94,6 +94,9 @@ impl BuildArgs {
                 let path = if joined.exists() { &joined } else { path };
                 files.extend(source_files_iter(path, MultiCompilerLanguage::FILE_EXTENSIONS));
             }
+            if files.is_empty() {
+                eyre::bail!("No source files found in specified build paths.")
+            }
         }
 
         let format_json = shell::is_json();

crates/forge/tests/cli/cmd.rs

@@ -2829,7 +2829,7 @@ Compiler run successful!
 "#]]);
 
     // Expect compilation to be skipped as no files have changed
-    cmd.arg("build").assert_success().stdout_eq(str![[r#"
+    cmd.forge_fuse().arg("build").assert_success().stdout_eq(str![[r#"
 No files changed, compilation skipped
 
 "#]]);
@@ -2952,6 +2952,14 @@ Compiler run successful!
 [SOLC_VERSION] [ELAPSED]
 Compiler run successful!
 
+"#]]);
+
+    // Fail if no source file found.
+    prj.clear();
+    cmd.forge_fuse();
+    cmd.args(["build", "test/Dummy.sol", "--force"]).assert_failure().stderr_eq(str![[r#"
+Error: No source files found in specified build paths.
+
 "#]]);
 });