Abseil pkgconfig leads to too many arguments

Including the pkgconfig from abseil results in hundreds of CFLAGS many of which are redundant. I believe they could be restructured to have one common pkconfig that is added to "requires" so the CFLAGS are only included once.

Here is an example of the CFLAGS that are repeated:
```
-DNOMINMAX
-Wno-float-conversion
-Wno-implicit-float-conversion
-Wno-implicit-int-float-conversion
-Wno-implicit-int-conversion
-Wno-shorten-64-to-32
-Wno-sign-conversion
-Wno-unknown-warning-option
```