Disable LLVM warnings and enable LTO in emscripten build (#487)

Fixed #148 and last task of #156

Author: kvpanch

crates/llvm-builder/src/platforms/wasm32_emscripten.rs

@@ -91,6 +91,7 @@ fn build_host(
                     target_directory.to_string_lossy()
                 ),
                 "-DLLVM_BUILD_SHARED_LIBS='Off'",
+                "-DLLVM_ENABLE_WARNINGS='Off'",
                 "-DCMAKE_BUILD_TYPE='Release'",
                 &format!(
                     "-DLLVM_TARGETS_TO_BUILD='WebAssembly;{}'",
@@ -152,10 +153,8 @@ fn build_target(
                 "Ninja",
                 "-DLINKER_SUPPORTS_COLOR_DIAGNOSTICS=0",
                 "-DCMAKE_BUILD_WITH_INSTALL_RPATH=1",
-                // Enable thin LTO but emscripten has various issues with it.
-                // FIXME: https://github.com/paritytech/revive/issues/148
-                //"-DLLVM_ENABLE_LTO='Thin'",
-                //"-DCMAKE_EXE_LINKER_FLAGS='-Wl,-u,htons -Wl,-u,htonl -Wl,-u,fileno -Wl,-u,ntohs'",
+                "-DLLVM_ENABLE_LTO='Thin'",
+                "-DCMAKE_EXE_LINKER_FLAGS='-Wl,-u,htons -Wl,-u,htonl -Wl,-u,fileno -Wl,-u,ntohs'",
                 &format!(
                     "-DCMAKE_INSTALL_PREFIX='{}'",
                     target_directory.to_string_lossy()