FindBoost: Update MSVC architecture check code style
Fixed problem with the 'FindBoost' module not locating binaries on Windows using the 'Versioned' layout scheme (V1.66 & later)
Changes were made to the binary file names in Boost 1.66 when built in 'Versioned' layout (the default). This introduced the 'x32' and 'x64' values for 32-bit and 64-bit binaries built with the x86 or x64 compiler Id.
When checking the property 'CMAKE_CXX_COMPILER_ARCHITECTURE_ID' with a STREQUAL operator quotes are required around it (as is the case for all other instances I could find). Added missing quotes when performing the string comparison operation.
Topic-rename: FindBoost-arch-check-style