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, 5 insertions, 2 deletions

diff --git a/.gitignore b/.gitignore
index 61fc41b..10ada7a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -33,6 +33,9 @@ DerivedData
 *.hmap
 *.ipa
 
+# IntelliJ
+.idea
+
 # Vim
 *.swo
 *.swp
@@ -56,5 +59,5 @@ Podfile.lock
 *.xcworkspace
 
 # CMake
-.downloads
-.idea/
+Debug
+Release