Add -j$(nproc) make option to speed up build time (#15928)

Adding `-j$(nproc)` reduces build time on the external dependencies by
approximately 25%.

virtualization/Docker/scripts/ssocr

@@ -18,7 +18,7 @@ git clone --depth 1 https://github.com/auerswal/ssocr.git ssocr
 cd ssocr/
 
 # Compile the library
-make
+make -j$(nproc)
 
 # Install the binaries/libraries to your local system (prefix is /usr/local)
-make install
+make install