Updated Compile from source in Linux (markdown)

Compile-from-source-in-Linux.md

@@ -364,6 +364,7 @@ git clone https://github.com/f4exb/sdrangel.git
 cd sdrangel
 mkdir build; cd build
 cmake -Wno-dev -DDEBUG_OUTPUT=ON -DRX_SAMPLE_24BIT=ON \
+-DCMAKE_BUILD_TYPE=RelWithDebInfo \
 -DMIRISDR_DIR=/opt/install/libmirisdr \
 -DAIRSPY_DIR=/opt/install/libairspy \
 -DAIRSPYHF_DIR=/opt/install/libairspyhf \