meson: remove -Db_pie=true -Db_staticpic=true args

[ibc]

• May fix Windows CI jobs failing due to meson #1292
• PIC flag was introduced in previous mediasoup gyp build system: bbc3514, it was needed for mediasoup to build on Ubuntu 18.04: unbuntu 18.04 release compile need cflags add '-fPIC' #315.
• No idea about the possible implications of this removal. Note that we no longer test mediasoup on Ubuntu 18.04 (oldest Ubuntu we test in CI is 20.04).

More details

In https://mesonbuild.com/Builtin-options.html#base-options:

The following options are available. Note that they may not be available on all platforms or with all compilers:
[...]

• b_staticpic: Build static libraries as position independent
• b_pie: Build position-independent executables (since 0.49.0)

Somewhere else:

Position-independent code is not tied to a specific address. This independence allows the code to execute efficiently at a different address in each process that uses the code. Position-independent code is recommended for the creation of shared objects.

On some architectures, including x86, -fPIC generates much worse code (i.e. a function call) for loads/stores of data. While this is tolerable for libraries, it is undesirable for executables.

If the object is to be linked as a shared library, or a static library that will in turn be linked in a shared library, use -fPIC. If the object is to be linked as a position indenpendent executable, or astatic library that will in turn be linked in position independent executable, use -fPIE.

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