Build and test both C++ loggers where possible (#595)

* Rename FIREBASE_BINARY_DIR to FIREBASE_INSTALL_DIR

  Make this consistent with the outer superbuild and also make the
  association with CMAKE_INSTALL_PREFIX more obvious.

* Build and test log_stdio separate from the rest of util

  This is in preparation for adding a test for log_apple

* Build and test log_apple under CMake

  Also add notes about how FIRLogger's debug mode can break this test

* Refactor log_apple to cut down duplicate switch statements

  There's also a slight reduction in final binary size.

1 files changed, 42 insertions, 1 deletions

diff --git a/Firestore/core/src/firebase/firestore/util/CMakeLists.txt b/Firestore/core/src/firebase/firestore/util/CMakeLists.txt
index ebb2301..d70397d 100644
--- a/Firestore/core/src/firebase/firestore/util/CMakeLists.txt
+++ b/Firestore/core/src/firebase/firestore/util/CMakeLists.txt
@@ -15,6 +15,47 @@
 add_library(
   firebase_firestore_util
   autoid.cc
-  log_stdio.cc
   secure_random_arc4random.cc
 )
+
+# log_stdio can be built and tested everywhere
+add_library(
+  firebase_firestore_util_log_stdio
+  log_stdio.cc
+)
+
+# log_apple can only built and tested on apple plaforms
+if(APPLE)
+  add_library(
+    firebase_firestore_util_log_apple
+    log_apple.mm
+  )
+  target_compile_options(
+    firebase_firestore_util_log_apple
+    PRIVATE
+    ${OBJC_FLAGS}
+  )
+  target_link_libraries(
+    firebase_firestore_util_log_apple
+    PUBLIC
+    FirebaseCore
+  )
+endif(APPLE)
+
+# Export a dependency on the correct logging library for this platform. All
+# buildable libraries are built and tested but only the best fit is exported.
+if(APPLE)
+  target_link_libraries(
+    firebase_firestore_util
+    PUBLIC
+    firebase_firestore_util_log_apple
+  )
+
+else(NOT APPLE)
+  target_link_libraries(
+    firebase_firestore_util
+    PUBLIC
+    firebase_firestore_util_log_stdio
+  )
+
+endif(APPLE)