Fix warning when building with CMake 3.23.

When building iceoryx_posh with CMake 3.23, it throws a warning:

Ignoring empty string ("") provided on the command line.

This happens because when CMAKE_TOOLCHAIN_FILE is not
defined, TOOLCHAIN_FILE is also not defined and thus is empty.
Workaround this new behavior by setting a variable that contains
a bunch of things, and may also *optionally* include the
define for the TOOLCHAIN file, which removes the warning.

Signed-off-by: Chris Lalancette <[email protected]>

Author: clalancette

iceoryx_posh/cmake/cpptoml/CMakeLists.txt

@@ -33,12 +33,6 @@ else()
     set(CREATE_PATH_COMMAND mkdir -p)
 endif()
 
-if(DEFINED CMAKE_TOOLCHAIN_FILE)
-    set(TOOLCHAIN_FILE "-DCMAKE_TOOLCHAIN_FILE=${CMAKE_TOOLCHAIN_FILE}")
-    set(cpptoml_DIR ${CMAKE_BINARY_DIR}/dependencies/install/lib/cmake/cpptoml)
-    set(cpptoml_DIR ${cpptoml_DIR} CACHE PATH "" FORCE)
-endif()
-
 # set download config, source and build paths
 set(DOWNLOAD_CONFIG_DIR ${CMAKE_BINARY_DIR}/dependencies/cpptoml/download)
 set(SOURCE_DIR ${CMAKE_BINARY_DIR}/dependencies/cpptoml/src)
@@ -72,14 +66,22 @@ if(result)
     message(WARNING "CMake step [patch] for cpptoml failed: ${result}! Build of cpptoml might fail")
 endif()
 
-execute_process(COMMAND ${CMAKE_COMMAND} -G "${CMAKE_GENERATOR}" "-DENABLE_LIBCXX=off" "-DCPPTOML_BUILD_EXAMPLES=off" "-DCMAKE_INSTALL_PREFIX=${INSTALL_DIR}" "${TOOLCHAIN_FILE}" "${SOURCE_DIR}"
-        "-DCMAKE_C_FLAGS_INIT=${CMAKE_C_FLAGS_INIT}"
-        "-DCMAKE_CXX_FLAGS_INIT=${CMAKE_CXX_FLAGS_INIT}"
-        "-DCMAKE_C_COMPILER=${CMAKE_C_COMPILER}"
-        "-DCMAKE_C_COMPILER_TARGET=${CMAKE_C_COMPILER_TARGET}"
-        "-DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}"
-        "-DCMAKE_CXX_COMPILER_TARGET=${CMAKE_CXX_COMPILER_TARGET}"
-        "-DCMAKE_LINKER=${CMAKE_LINKER}"
+set(CMAKE_ADDITIONAL_OPTIONS
+    "-DCMAKE_C_FLAGS_INIT=${CMAKE_C_FLAGS_INIT}"
+    "-DCMAKE_CXX_FLAGS_INIT=${CMAKE_CXX_FLAGS_INIT}"
+    "-DCMAKE_C_COMPILER=${CMAKE_C_COMPILER}"
+    "-DCMAKE_C_COMPILER_TARGET=${CMAKE_C_COMPILER_TARGET}"
+    "-DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}"
+    "-DCMAKE_CXX_COMPILER_TARGET=${CMAKE_CXX_COMPILER_TARGET}"
+    "-DCMAKE_LINKER=${CMAKE_LINKER}")
+
+if(DEFINED CMAKE_TOOLCHAIN_FILE)
+    list(APPEND CMAKE_ADDITIONAL_OPTIONS "-DCMAKE_TOOLCHAIN_FILE=${CMAKE_TOOLCHAIN_FILE}")
+    set(cpptoml_DIR ${CMAKE_BINARY_DIR}/dependencies/install/lib/cmake/cpptoml)
+    set(cpptoml_DIR ${cpptoml_DIR} CACHE PATH "" FORCE)
+endif()
+
+execute_process(COMMAND ${CMAKE_COMMAND} -G "${CMAKE_GENERATOR}" "-DENABLE_LIBCXX=off" "-DCPPTOML_BUILD_EXAMPLES=off" "-DCMAKE_INSTALL_PREFIX=${INSTALL_DIR}" "${SOURCE_DIR}" ${CMAKE_ADDITIONAL_OPTIONS}
     RESULT_VARIABLE result
     WORKING_DIRECTORY ${BUILD_DIR} )
 if(result)