Update modbus.cmake

Author: NikolasK-source

modbus.cmake

@@ -18,8 +18,8 @@ ExternalProject_Add(
         SOURCE_DIR ${MODBUS_DIR}
         DOWNLOAD_COMMAND cd ${MODBUS_DIR} && git clean -dfX
         CONFIGURE_COMMAND cd ${MODBUS_DIR} && git clean -dfX && ${MODBUS_DIR}/autogen.sh && ${MODBUS_DIR}/configure --srcdir=${MODBUS_DIR} --prefix=${MODBUS_BIN} --enable-static=yes --disable-shared
-        BUILD_COMMAND make
-        INSTALL_COMMAND make install
+        BUILD_COMMAND cd ${MODBUS_DIR} && make
+        INSTALL_COMMAND cd ${MODBUS_DIR} && make install
         BUILD_BYPRODUCTS ${MODBUS_STATIC_LIB}
 )