Made build.sh more portable

Author: Ithanil

build.sh

@@ -1,6 +1,11 @@
 #!/bin/sh
+
 . ./config.sh
-mkdir -p build
-cd build
+mkdir -p build && cd build
 cmake -DCMAKE_CXX_COMPILER="${CXX_COMPILER}" -DUSER_CXX_FLAGS="${CXX_FLAGS}" -DUSE_COVERAGE="${USE_COVERAGE}" ..
-make -j$(nproc)
+
+if [ "$1" == "" ]; then
+  make -j$(nproc 2>/dev/null || sysctl -n hw.ncpu 2>/dev/null || getconf _NPROCESSORS_ONLN 2>/dev/null)
+else
+  make -j$1
+fi