vcpkg build fixes, attempt 2/2

'vcpkg install io2d' was not working when building a Debug copy of io2d,
as 'd'ebug versions of certain libraries, namely Cairo, LibPNG, and
zlib, could not be found.  Each of those libraries, on Windows, had
different library names, if and when a Debug copy was used.  For
example, "cairod" for Debug, "cairo" for Release.  When building the
Debug copy of io2d, it would not find the 'd' versions of these
libraries, which caused CMake to fail during its 'config' stage.  The Release copy of io2d would pass cmake configuration, but not the Debug copy.

Fix attempt 1, which is-being (or by now, perhaps, has-been) rescinded,
tried to ignore 'd' versions of libraries.  This got 'vcpkg install
io2d' working, however it caused problems when building and running
io2d standalone, using older build instructions (that involved running
CMake manually, then building io2d.sln manually).  The problems involved
.dll files that could not be found.

Fix attempt 2 (this one!), does two things:
 1. it doesn't attempt to directly link to LibPNG and zlib, when using
 MSVC.  This is unnecessary, as GraphicsMagick is suitably-used instead.
 2. for Cairo, it looks for both 'd' (Debug) and not-'d' (Release)
 libraries, however, if the 'd' version is not found, it'll fall back to
 using the not-'d' version.

The two things above combine to allow vcpkg to successfully configure,
then build io2d, while allowing io2d to also be built manually.

Author: DavidLudwig

P0267_RefImpl/P0267_RefImpl/cairo/CMakeLists.txt

@@ -46,7 +46,12 @@ target_include_directories(io2d_cairo SYSTEM PUBLIC ${CAIRO_INCLUDE_DIR} ${GRAPH
 target_link_libraries(io2d_cairo PUBLIC ${GRAPHICSMAGICK_LIB})
 
 if(MSVC)
-	target_link_libraries(io2d_cairo PUBLIC debug ${CAIRO_LIB_DEBUG} optimized ${CAIRO_LIB_RELEASE})
+	if(CAIRO_LIB_DEBUG STREQUAL "CAIRO_LIB_DEBUG-NOTFOUND")
+		message(STATUS "io2d: Can't find Debug build of Cairo. Will try to use Release build, instead.")
+		target_link_libraries(io2d_cairo PUBLIC ${CAIRO_LIB_RELEASE})
+	else()
+		target_link_libraries(io2d_cairo PUBLIC debug ${CAIRO_LIB_DEBUG} optimized ${CAIRO_LIB_RELEASE})
+	endif()
 else()
 	target_link_libraries(io2d_cairo PUBLIC ${CAIRO_LIB})
 endif()

P0267_RefImpl/P0267_RefImpl/cairo/win32/CMakeLists.txt

@@ -30,20 +30,14 @@ if(MSVC)
 	find_library(FREETYPE_LIB freetype)
 	find_library(FONTCONFIG_LIB fontconfig)
 	find_library(BZ_LIB bz2)
-	find_library(ZLIB_LIB_DEBUG zlibd)
-	find_library(ZLIB_LIB_RELEASE zlib)
 	find_library(JPEG_LIB jpeg)
-	find_library(PNG_LIB_DEBUG libpng16d)
-	find_library(PNG_LIB_RELEASE libpng16)
 	find_library(TIFF_LIB tiff)
 	find_library(EXPAT_LIB expat)
 	find_library(LZMA_LIB lzma)
 	find_library(ICONV_LIB libiconv)
 	find_library(CHARSET_LIB libcharset)
 
 	target_link_libraries(io2d_cairo_win32 PUBLIC ${PIXMAN_LIB} ${FREETYPE_LIB} ${FONTCONFIG_LIB} ${BZ_LIB} ${JPEG_LIB} ${TIFF_LIB} ${EXPAT_LIB} ${LZMA_LIB} ${ICONV_LIB} ${CHARSET_LIB})
-	target_link_libraries(io2d_cairo_win32 PUBLIC debug ${PNG_LIB_DEBUG} optimized ${PNG_LIB_RELEASE})
-	target_link_libraries(io2d_cairo_win32 PUBLIC debug ${ZLIB_LIB_DEBUG} optimized ${ZLIB_LIB_RELEASE})
 endif()
 
 install(