[util][build] Add UUID generation methods

Links to libuuid on Linux, which comes with util-linux. On Windows it
uses rpc.h's UuidCreate method.

UUIDs will be used as globally unique preset identifiers.

CMakeLists.txt

@@ -29,6 +29,7 @@ file(GLOB SRC_FILES_AVS_COMMON
     avs/vis_avs/video.cpp
     avs/vis_avs/video_libav.cpp
     avs/platform.c
+    avs/uuid.cpp
     avs/3rdparty/md_fft.cpp
 )
 
@@ -211,7 +212,7 @@ elseif(LINUX)
     include(FindPkgConfig)
     pkg_search_module(PIPEWIRE REQUIRED libpipewire-0.3)
     target_include_directories(avs_common PUBLIC ${PIPEWIRE_INCLUDE_DIRS})
-    target_link_libraries(libavs ${PIPEWIRE_LIBRARIES})
+    target_link_libraries(libavs ${PIPEWIRE_LIBRARIES} uuid)
     target_link_options(libavs PUBLIC -Wl,-m elf_i386)
     set(AVS_DYLIB_EXTENSION "so")
     add_executable(avs-cli avs/avs-cli.c)

avs/uuid.cpp

@@ -0,0 +1,24 @@
+#include "uuid.h"
+
+#ifdef _WIN32
+#include <rpc.h>
+#elif defined __linux__
+#include <uuid/uuid.h>
+#endif
+
+std::string uuid4() {
+    auto uuid_str = (char*)malloc(37);
+    uuid_str[36] = '\0';
+#ifdef _WIN32
+    UUID uuid;
+    UuidCreate(&uuid);
+    UuidToString(&uuid, (unsigned char**)&uuid_str);
+#elif defined __linux__
+    uuid_t uuid;
+    uuid_generate(uuid);
+    uuid_unparse_lower(uuid, uuid_str);
+#endif
+    auto retval = std::string(uuid_str);
+    free(uuid_str);
+    return retval;
+}

avs/uuid.h

@@ -0,0 +1,3 @@
+#include <string>
+
+std::string uuid4();