Add URDE_VECTOR_ISA=native, update README.md with CMake options

CMakeLists.txt

@@ -104,7 +104,10 @@ else()
     #add_compile_definitions(_GLIBCXX_DEBUG=1)
   endif()
 
-  if(${URDE_VECTOR_ISA} STREQUAL "avx2")
+  if(${URDE_VECTOR_ISA} STREQUAL "native")
+    add_compile_options(-march=native)
+    message(STATUS "Building with native ISA")
+  elseif(${URDE_VECTOR_ISA} STREQUAL "avx2")
     add_compile_options(-mavx2)
     message(STATUS "Building with AVX2 Vector ISA")
   elseif(${URDE_VECTOR_ISA} STREQUAL "avx")

README.md

@@ -41,9 +41,14 @@ cd urde-build
 
 ```sh
 cmake -DCMAKE_BUILD_TYPE=Debug ../urde
-make
+make -j$(nproc)
 ```
 
+CMake options:
+- Build release optimized (better runtime performance): `-DCMAKE_BUILD_TYPE=Release`
+- Use clang+lld (faster linking): `-DCMAKE_C_COMPILER=/usr/bin/clang -DCMAKE_CXX_COMPILER=/usr/bin/clang++`
+- Optimize for current CPU (resulting binaries are not portable): `-DURDE_VECTOR_ISA=native`
+
 #### Qt Creator
 *(main development / debugging IDE)*