Resolve erroneous clang-tidy warning about using a moved from pointer

The clang-tidy warning `clang-analyzer-cplusplus.Move` warns when a
moved from object is deferenced. This is triggered in spdlog because
clang-tidy fails to detect that the `logger:set_formatter` will only
move the unique_ptr on the last iteration of the loop, assuming that
`f->clone` may be called on it afterwards.

To fix, add a break statement after moving the pointer (on the last
iteration) to let clang-tidy know the logger pointer is not used after
this point.

only include windows.h when it's unavoidable

Updates supporting CPack RPM generation

Enable command line overrides of default settings
* CPACK_GENERATOR
* CPACK_PACKAGE_RELOCATABLE

Enables command line setting of generated RPM version attributes
* CPACK_RPM_PACKAGE_RELEASE
* CPACK_RPM_PACKAGE_ARCHITECTURE

Adds dependency on pkgconfig RPM when not generating relocatable RPM

Add example to FMT_STRING in README

Fix Windows event log sink

workaround for `Unknown extension ".c" for file` issue

http://www.grokit.ca/cnt/CMakeProblemsSolutions/