Made it easier to use the library with external zstdlib implementatio…

…ns (mostly in non CMake builds).

In our internal repository, we have our own version of zstdlib and introducing extra copy is both undesirable and potentially dangerous (due to ODR violations).

Co-authored-by: Rémi Verschelde <rverschelde@gmail.com>

CMakeLists.txt

@@ -161,6 +161,7 @@ add_executable(basisu ${BASISU_SRC_LIST})
 
 if (ZSTD)
 	target_compile_definitions(basisu PRIVATE BASISD_SUPPORT_KTX2_ZSTD=1)
+	target_include_directories(basisu PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/zstd)
 else()
 	target_compile_definitions(basisu PRIVATE BASISD_SUPPORT_KTX2_ZSTD=0)
 endif()

encoder/basisu_comp.cpp

@@ -28,7 +28,7 @@
 #endif
 
 #if BASISD_SUPPORT_KTX2_ZSTD
-#include "../zstd/zstd.h"
+#include <zstd.h>
 #endif
 
 // Set to 1 to disable the mipPadding alignment workaround (which only seems to be needed when no key-values are written at all)

transcoder/basisu_transcoder.cpp

@@ -155,7 +155,7 @@
    // If BASISD_SUPPORT_KTX2_ZSTD is 0, UASTC files compressed with Zstd cannot be loaded.
 	#if BASISD_SUPPORT_KTX2_ZSTD
 		// We only use two Zstd API's: ZSTD_decompress() and ZSTD_isError()
-		#include "../zstd/zstd.h"
+		#include <zstd.h>
 	#endif
 #endif