Address PR comments by adding some comments and making a few minor changes.

Author: jonsimantov

CMakeLists.txt

@@ -186,7 +186,7 @@ if(DESKTOP)
   set(OPENSSL_USE_STATIC_LIBS TRUE)
   if (MSVC)
     # Get the correct version of the OpenSSL libraries based on building for MT.
-    if ("${CMAKE_CXX_FLAGS_DEBUG}" MATCHES "/MT" OR
+    if ("${CMAKE_CXX_FLAGS_DEBUG}" MATCHES "/MTd" OR
         "${CMAKE_CXX_FLAGS_RELEASE}" MATCHES "/MT")
       set(OPENSSL_MSVC_STATIC_RT TRUE)
     else()
@@ -202,21 +202,25 @@ if(DESKTOP)
   # The call below to build_external_dependencies will make sure that these
   # libraries exist before the libraries are imported via add_library.
   if (MSVC)
-    set(OPENSSL_SSL_LIBRARY ${BORINGSSL_BINARY_DIR}/ssl/${CMAKE_BUILD_TYPE}/ssl.lib CACHE FILEPATH "" FORCE)
-    set(OPENSSL_CRYPTO_LIBRARY ${BORINGSSL_BINARY_DIR}/crypto/${CMAKE_BUILD_TYPE}/crypto.lib CACHE FILEPATH "" FORCE)
+    if (CMAKE_BUILD_TYPE)
+      set(BORINGSSL_LIB_SUBDIR "${CMAKE_BUILD_TYPE}")
+    else()
+      set(BORINGSSL_LIB_SUBDIR "Debug")
+    endif()
+    set(OPENSSL_SSL_LIBRARY ${BORINGSSL_BINARY_DIR}/ssl/${BORINGSSL_LIB_SUBDIR}/ssl.lib CACHE FILEPATH "" FORCE)
+    set(OPENSSL_CRYPTO_LIBRARY ${BORINGSSL_BINARY_DIR}/crypto/${BORINGSSL_LIB_SUBDIR}/crypto.lib CACHE FILEPATH "" FORCE)
   else()
     set(OPENSSL_SSL_LIBRARY ${BORINGSSL_BINARY_DIR}/ssl/libssl.a CACHE FILEPATH "" FORCE)
     set(OPENSSL_CRYPTO_LIBRARY ${BORINGSSL_BINARY_DIR}/crypto/libcrypto.a CACHE FILEPATH "" FORCE)
   endif()
 endif()
 
-if(NOT FIREBASE_CPP_USE_PRIOR_GRADLE_BUILD)
+
+if(DESKTOP)
   message(STATUS "Building external project dependencies...")
   build_external_dependencies()
   message(STATUS "Build of external project dependencies complete.")
-endif()
-
-if(DESKTOP)
+  
   set(OPENSSL_FOUND TRUE CACHE BOOL "" FORCE)
   set(OPENSSL_NO_ASM TRUE)  # Force cross-platform BoringSSL, no ASM.
   set(OPENSSL_INCLUDE_DIR ${BORINGSSL_ROOT_DIR}/include CACHE PATH "" FORCE)
@@ -299,6 +303,7 @@ if(DESKTOP)
   # Build curl as a static library
   set(CURL_STATICLIB ON CACHE BOOL "")
   if (WIN32)
+    # Enable Windows native SSL/TLS in libcurl.
     set(CMAKE_USE_SCHANNEL ON CACHE BOOL "")
   endif()
 

cmake/external/boringssl.cmake

@@ -36,4 +36,4 @@ ExternalProject_Add(
   BUILD_COMMAND     ""
   INSTALL_COMMAND   ""
   TEST_COMMAND      ""
-)
+)

cmake/external_rules.cmake

@@ -93,7 +93,7 @@ function(download_external_sources)
     WORKING_DIRECTORY ${PROJECT_BINARY_DIR}/external
   )
 
-  if(NOT ANDROID AND NOT IOS)
+  if(external_platform EQUALS "DESKTOP")
     # CMake's find_package(OpenSSL) doesn't quite work right with BoringSSL
     # unless the header file contains OPENSSL_VERSION_NUMBER.
     file(READ ${PROJECT_BINARY_DIR}/external/src/boringssl/src/include/openssl/opensslv.h TMP_HEADER_CONTENTS)
@@ -127,9 +127,9 @@ function(build_external_dependencies)
     set(ENV_COMMAND env -i PATH=${firebase_command_line_path} HOME=${firebase_command_line_home} )
   endif()
 
-  message("CMake generator: ${CMAKE_GENERATOR}")
-  message("CMake generator platform: ${CMAKE_GENERATOR_PLATFORM}")
-  message("CMake toolchain file: ${CMAKE_TOOLCHAIN_FILE}")
+  message(STATUS "CMake generator: ${CMAKE_GENERATOR}")
+  message(STATUS "CMake generator platform: ${CMAKE_GENERATOR_PLATFORM}")
+  message(STATUS "CMake toolchain file: ${CMAKE_TOOLCHAIN_FILE}")
 
   set(CMAKE_SUB_CONFIGURE_OPTIONS -G "${CMAKE_GENERATOR}")
   set(CMAKE_SUB_BUILD_OPTIONS)
@@ -207,8 +207,8 @@ function(build_external_dependencies)
           -DCMAKE_TOOLCHAIN_FILE=${CMAKE_TOOLCHAIN_FILE})
     endif()
   endif()
-  message("Sub-configure options: ${CMAKE_SUB_CONFIGURE_OPTIONS}")
-  message("Sub-build options: ${CMAKE_SUB_BUILD_OPTIONS}")
+  message(STATUS "Sub-configure options: ${CMAKE_SUB_CONFIGURE_OPTIONS}")
+  message(STATUS "Sub-build options: ${CMAKE_SUB_BUILD_OPTIONS}")
 
   if(NOT ANDROID AND NOT IOS)
     execute_process(