Add googletest wrap

Add the wrap so tests can be done standalone.

The "'BUILD_SHARED_LIBS': 'ON'" option is needed or else stdplus, which
is indirectly pulled in as a subproject, fails with:

```
s

Add googletest wrap

Add the wrap so tests can be done standalone.

The "'BUILD_SHARED_LIBS': 'ON'" option is needed or else stdplus, which
is indirectly pulled in as a subproject, fails with:

```
subprojects/stdplus/src/meson.build:207:22: ERROR: Can't link non-PIC static library 'gtest' into shared library 'stdplus-gtest'.
Use the 'pic' option to static_library to build with PIC.
```

Change-Id: Ia1847cab885e2b6adb72bec08621f5d154990e79
Signed-off-by: Matt Spinler <spinler@us.ibm.com>

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