tests/lib/cpp/cxx: remove inline comments from DTS-generated headers

The DTS extraction process generates headers with inline comments, which
are not supported by the C preprocessor. This is causing build failures
when using the generated headers in C++ code.

Signed-off-by: Luca Burelli<[email protected]>

Author: pillo79

tests/lib/cpp/cxx/CMakeLists.txt

@@ -1,5 +1,16 @@
 # SPDX-License-Identifier: Apache-2.0
 
+# C++ support is enabled by prj.conf, but since Kconfig options are processed
+# after the DTS extraction, the following argument must be passed manually to
+# avoid issues like:
+#
+#     zephyr/devicetree_generated.h:2155:95: error: pasting "/* 0x58022400 */" and "U"
+#                                                   does not give a valid preprocessing token
+#     2155 | #define DT_N_S_soc_S_<...>_REG_IDX_0_VAL_ADDRESS 1476535296 /* 0x58022400 */
+#                                                                        ^~~~~~~~~~~~~~~~
+#
+set(EXTRA_GEN_DEFINES_ARGS --no-inline-comments)
+
 cmake_minimum_required(VERSION 3.20.0)
 find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
 project(cpp)