Fix CMake architecture string comparison.
Fix CMake architecture string comparison.

EQUAL compares numeric values. Use STREQUAL instead.

Also clarify the macro for setting the export map / version script.

Bug b/110884149

Change-Id: If30c31d17ad35684a8c637b3619bdd0b90be6f2d
Reviewed-on: https://swiftshader-review.googlesource.com/19709
Reviewed-by: Alexis Hétu <1c7141772178a7e80858c3db5052b328076f08f4@google.com>
Tested-by: Nicolas Capens <51edc787c30f24c4904e8ffbb5523c3a9f7a451d@google.com>

bkaradzic/SwiftShader,bkaradzic/SwiftShader,google/swiftshader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,google/swiftshader,google/swiftshader