Fix loongarch64 atomic build error

[zhaixiaojuan]

Dear maintainer，
The LoongArch architecture (LoongArch) is an Instruction Set Architecture (ISA) that has a RISC style.
Documentations:
ISA:
https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html
ABI:
https://loongson.github.io/LoongArch-Documentation/LoongArch-ELF-ABI-EN.html
More docs can be found at:
https://loongson.github.io/LoongArch-Documentation/README-EN.html

When I execute the following command on a loongarch64 debian environment：

PKG_CONFIG=/usr/bin/pkg-config cmake -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_BUILD_TYPE=None -DCMAKE_INSTALL_SYSCONFDIR=/etc -DCMAKE_INSTALL_LOCALSTATEDIR=/var -DCMAKE_EXPORT_NO_PACKAGE_REGISTRY=ON -DCMAKE_FIND_USE_PACKAGE_REGISTRY=OFF -DCMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY=ON -DFETCHCONTENT_FULLY_DISCONNECTED=ON "-GUnix Makefiles" -DCMAKE_VERBOSE_MAKEFILE=ON -DCMAKE_INSTALL_LIBDIR=lib/loongarch64-linux-gnu -DCMAKE_INSTALL_PREFIX=/opt/ros/jazzy -DAMENT_PREFIX_PATH=/opt/ros/jazzy -DCMAKE_PREFIX_PATH=/opt/ros/jazzy
make -j1 VERBOSE=1

I get an error:

[100%] Linking CXX executable pal_statistics-test
/usr/bin/cmake -E cmake_link_script CMakeFiles/pal_statistics-test.dir/link.txt --verbose=1
/usr/bin/ld: libpal_statistics.so: undefined reference to `__atomic_store_16'      
/usr/bin/ld: libpal_statistics.so: undefined reference to `__atomic_load_16'    
/usr/bin/ld: libpal_statistics.so: undefined reference to `__atomic_compare_exchange_16'  

I submitted a fix for the above problem and completed the test verification locally.

[zhaixiaojuan]

Hi, is there any latest progress on this PR?

[kimdoyoung0319]

A build for RISC-V suffers with same problem. It would be nice to link libatomic for both loongarch and RISC-V (if it is merged).

[christophfroehlich]

@saikishor 👀

[saikishor]

Hello!

I completely missed this one. We will try to take a look at this, Thanks for reporting

[saikishor]

@zhaixiaojuan Can you test @mathias-luedtke's fix in the branch https://github.com/pal-robotics/pal_statistics/tree/fix/link-atomic

Let us know if it works for you

[zhaixiaojuan]

@saikishor

Let us know if it works for you

Okay, I'll test it now.

[saikishor]

@zhaixiaojuan Thank you!

[zhaixiaojuan]

Hi, @saikishor
Great, I tested it locally and it solved the problem.