fixed cmake command

src/docs/part1/simple_detector.md

@@ -43,7 +43,7 @@ directories named compact (but not always).
 ### Compile the detector library
 
 ```bash
-cmake -B build -DCMAKE_INSTALL_PREFIX=../local/ -S . -DCMAKE_CXX_STANDARD=17
+cmake -B build -S . -DCMAKE_INSTALL_PREFIX=../local/ -DCMAKE_CXX_STANDARD=17
 cmake --build build -j4 -- install
 ```
 

src/docs/part2/adding_detectors.md

@@ -16,9 +16,8 @@ cd part2
 ### Compile the detector library
 
 ```bash
-mkdir build
-cmake ../. -DCMAKE_INSTALL_PREFIX=../../local 
-make -j4 install
+cmake -B build -S . -DCMAKE_INSTALL_PREFIX=../local/ -DCMAKE_CXX_STANDARD=17
+cmake --build build -j4 -- install
 ```