pw_build: Fix source compilation in CMake facades
pw_build: Fix source compilation in CMake facades

Compile source files in the main library instead of the .facade library.

Change-Id: Ie3d75deeb59434fc9e0023b5c82f3b23d9feb247
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/28681
Reviewed-by: Alexei Frolov <a1b001416a8cf9aaea32a3411f8f3c0793ebc0b5@google.com>
Commit-Queue: Auto-Submit <14637eda5603879df170705285bf30f5996692f0@pigweed.google.com.iam.gserviceaccount.com>
Pigweed-Auto-Submit: Wyatt Hepler <cca3bedb37979eacd157a9bceb473582df8aea1e@google.com>

google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed