Fix sed command in DEVELOPER_GUIDE to append a new line character '\n'.

Signed-off-by: Dooyong Kim <[email protected]>

DEVELOPER_GUIDE.md

@@ -119,7 +119,8 @@ export CXX=/opt/homebrew/opt/llvm/bin/clang++
 // In case of linking issues with the external libraries and clang, you can try setting the CMAKE compiler to gcc/g++ instead through the following commands:
 export CC=gcc
 export CXX=g++
-sed -i '' '/set(CMAKE_CXX_STANDARD_REQUIRED True)/a\'$'\n''set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Xclang -fopenmp -L/opt/homebrew/opt/libomp/lib -I/opt/homebrew/opt/libomp/include -lomp -arch arm64 -fexceptions")' CMakeLists.txt
+sed -i '' '/set(CMAKE_CXX_STANDARD_REQUIRED True)/a\'$'\n''set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Xclang -fopenmp -L/opt/homebrew/opt/libomp/lib -I/opt/homebrew/opt/libomp/include -lomp -arch arm64 -fexceptions")'$'\n''' CMakeLists.txt
+
 
 // Build
 cmake . --fresh
@@ -478,4 +479,4 @@ The Github workflow in [`backport.yml`](.github/workflows/backport.yml) creates
 original PR with an appropriate label `backport <backport-branch-name>` is merged to main with the backport workflow 
 run successfully on the PR. For example, if a PR on main needs to be backported to `1.x` branch, add a label 
 `backport 1.x` to the PR and make sure the backport workflow runs on the PR along with other checks. Once this PR is 
-merged to main, the workflow will create a backport PR to the `1.x` branch.
+merged to main, the workflow will create a backport PR to the `1.x` branch.