cmake: added some comments about eagle/excelsior

cmake/configs/posix_eagle_default.cmake

@@ -1,7 +1,10 @@
+# The Eagle board is the first generation Snapdragon Flight board by Qualcomm.
+#
+# This cmake config builds for POSIX, so the part of the flight stack running
+# on the Linux side of the Snapdragon.
 include(configs/posix_sdflight_default)
 
-# This definition allows to differentiate if this just the usual POSIX build
-# or if it is for the Snapdragon.
+# This definition allows to differentiate the specific board.
 add_definitions(
 	-D__PX4_POSIX_EAGLE
-	)
+)

cmake/configs/posix_excelsior_default.cmake

@@ -1,5 +1,10 @@
+# Excelsior is the code name of a board currently in development.
+#
+# This cmake config builds for POSIX, so the part of the flight stack running
+# on the Linux side of the Snapdragon.
 include(configs/posix_sdflight_default)
+
+# This definition allows to differentiate the specific board.
 add_definitions(
 	-D__PX4_POSIX_EXCELSIOR
-)
-
+)