Fix C++ exception handling on NIOS2

[stephanosio]

Summary

nios2: Fix C++ exception handling info linking

The NIOS2 architecture linker script was including `cplusplus-ram.ld`
linker script after `__data_ram_end`, and this caused the content of
`.gcc_except_table` section to be not copied to the RAM by the
`z_data_copy` function; leading to the C++ exception handling
malfunction.

This commit relocates the `cplusplus-ram.ld` linker script inclusion
such that the contents of the relevant sections are properly copied by
the `z_data_copy` function.

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>

Test Result

[110/111] Linking CXX executable zephyr/zephyr.elf
Memory region         Used Size  Region Size  %age Used
           RESET:          0 GB         32 B      0.00%
           FLASH:      158544 B   16777184 B      0.94%
            SRAM:       10824 B   16777184 B      0.06%
        IDT_LIST:          0 GB         2 KB      0.00%
[110/111] To exit from QEMU enter: 'CTRL+a, x'[QEMU] CPU: nios2
        cpu->env.reset_addr:            0
        cpu->env.exception_addr:        400020
*** Booting Zephyr OS build v2.6.0-rc2-57-g053ff6fa0e72  ***
version 201703
Running test suite libcxx_tests
===================================================================
START - test_array
 PASS - test_array in 0.0 seconds
===================================================================
START - test_vector
 PASS - test_vector in 0.0 seconds
===================================================================
START - test_make_unique
 PASS - test_make_unique in 0.0 seconds
===================================================================
START - test_exception
 PASS - test_exception in 0.0 seconds
===================================================================
Test suite libcxx_tests succeeded
===================================================================
PROJECT EXECUTION SUCCESSFUL

Note that, in order to test this in qemu_nios2, you must do so with a patched QEMU: see #35772 (comment).

Fixes #35772.

[galak]

we probably need to platform_exclude: qemu_nios2 here.

[stephanosio]

For the time being, twister automatically skips any tests with FLASH overflow and treats it as a non-failure. Also, If we ever manage to slim down Zephyr such that it can fit into the current 128KB flash, it will pass anyway.

stephanos@devworx1:~/Dev/zephyrproject/zephyr$ scripts/twister -v -N -s tests/subsys/cpp/libcxx/cpp.libcxx.exceptions -p qemu_nios2
ZEPHYR_BASE unset, using "/home/stephanos/Dev/zephyrproject/zephyr"
Renaming output directory to /home/stephanos/Dev/zephyrproject/zephyr/twister-out.14
INFO    - Zephyr version: v2.6.0-rc2-57-g053ff6fa0e72
INFO    - JOBS: 60
INFO    - Using 'zephyr' toolchain.
INFO    - Building initial testcase list...
INFO    - 1 test scenarios (1 configurations) selected, 0 configurations discarded due to filters.
INFO    - Adding tasks to the queue...
INFO    - Added initial list of jobs to queue
INFO    - 1/1 qemu_nios2                tests/subsys/cpp/libcxx/cpp.libcxx.exceptions      SKIPPED (FLASH overflow)

INFO    - 0 of 0 test configurations passed (0.00%), 0 failed, 1 skipped with 0 warnings in 11.06 seconds
INFO    - In total 0 test cases were executed, 4 skipped on 1 out of total 372 platforms (0.27%)
INFO    - 0 test configurations executed on platforms, 0 test configurations were only built.
INFO    - Saving reports...
INFO    - Writing xunit report /home/stephanos/Dev/zephyrproject/zephyr/twister-out/twister.xml...
INFO    - Writing xunit report /home/stephanos/Dev/zephyrproject/zephyr/twister-out/twister_report.xml...
INFO    - Run completed

In that sense, I doubt it is necessary to platform_exclude: qemu_nios2 here.

@nashif any comments on this?

[galak]

Ok, if that's the case than no issues.

[galak]

Probably need to exclude qemu_nios2 from the test. Can you add a comment that qemu6 as expected in SDK 0.13.0 should fix that.