Add UA_ENABLE_INTERPROCEDURAL_OPTIMIZATION CMake option to disable interprocedural optimization

[traversaro]

Description

After #1732 , the CMAKE_INTERPROCEDURAL_OPTIMIZATION global CMake option is always enabled if the compiler supports it. In gcc, this adds the -flto flag, that cannot be removed via UA_ARCH_REMOVE_FLAGS because it is added by CMake itself.
However, in some cases you may want to disable IPO even if your compilers supports it, for example if your linker has problem with it. In those cases, it would be convenient to have a UA_ENABLE_INTERPROCEDURAL_OPTIMIZATION CMake option, that by default is ON and that would permit to disable the IPO.

If you are ok with this idea, I would be happy to open a PR implementing it.

Checklist

Please provide the following information:

• open62541 Version (release number or git tag): v1.0
• Other OPC UA SDKs used (client or server):
• Operating system:
• Logs (with UA_LOGLEVEL set as low as necessary) attached
• Wireshark network dump attached
• Self-contained code example attached
• Critical issue: no

[jpfr]

I'm hesitant to put in a build flag for everything.
We should use CMake defaults and keep the build system as simple as possible.

I'd prefer either of the following

• The CheckIPOSupported CMake package could already provide manual overrides
• Local patching of the CMakeLists.txt