build: tidy up Makefile.inc use in lib and src

- cmake: use `CURL_RCFILES` instead of literal.
- cmake: use `LIB_RCFILES` instead of literal.
- cmake: fix comments.
- autotools: use `CURL_RCFILES` in `EXTRA_DIST`.
- autotools: use `LIB_RCFILES` in `EXTRA_DIST`.
- autotools: fix comments.
- autotools: fix indentation.

Closes #17694

src/CMakeLists.txt

@@ -66,12 +66,12 @@ if(CURL_CA_EMBED_SET)
   endif()
 endif()
 
-# Get CURL_CFILES, CURLX_CFILES, CURL_HFILES variables
+# Get CURL_FILES, CURL_CFILES, CURL_HFILES, CURLX_CFILES, CURLX_HFILES, CURL_RCFILES variables
 curl_transform_makefile_inc("Makefile.inc" "${CMAKE_CURRENT_BINARY_DIR}/Makefile.inc.cmake")
 include("${CMAKE_CURRENT_BINARY_DIR}/Makefile.inc.cmake")
 
 if(WIN32)
-  list(APPEND CURL_CFILES "curl.rc")
+  list(APPEND CURL_CFILES ${CURL_RCFILES})
 endif()
 
 if(BUILD_STATIC_CURL)

src/Makefile.am

@@ -26,8 +26,11 @@ AUTOMAKE_OPTIONS = foreign nostdinc
 # remove targets if the command fails
 .DELETE_ON_ERROR:
 
+# Get CURL_FILES, CURL_CFILES, CURL_HFILES, CURLX_CFILES, CURLX_HFILES, CURL_RCFILES variables
+include Makefile.inc
+
 EXTRA_DIST = mk-file-embed.pl mkhelp.pl \
- curl.rc Makefile.inc CMakeLists.txt .checksrc
+  $(CURL_RCFILES) Makefile.inc CMakeLists.txt .checksrc
 
 # Specify our include paths here, and do it relative to $(top_srcdir) and
 # $(top_builddir), to ensure that these paths which belong to the library
@@ -65,9 +68,6 @@ if USE_UNICODE
 UNICODEFLAG = -municode
 endif
 
-# Get CURL_CFILES, CURLX_CFILES, CURL_HFILES variables
-include Makefile.inc
-
 curl_cfiles_gen =
 curl_hfiles_gen =
 CLEANFILES =
@@ -86,7 +86,6 @@ nodist_curl_SOURCES = curltool_unity.c
 curl_SOURCES =
 CLEANFILES += curltool_unity.c
 else
-# CURL_FILES comes from Makefile.inc
 curl_SOURCES = $(CURL_FILES) $(curl_cfiles_gen) $(curl_hfiles_gen)
 endif
 if HAVE_WINDRES