configure: add option to statically link to libvulkan

This may be useful in weird setups and on platforms where
static linking to libvulkan is supported.

libplacebo also has this fallback.

configure

@@ -363,6 +363,7 @@ External library support:
   --disable-vdpau          disable Nvidia Video Decode and Presentation API for Unix code [autodetect]
   --disable-videotoolbox   disable VideoToolbox code [autodetect]
   --disable-vulkan         disable Vulkan code [autodetect]
+  --enable-vulkan-static   statically link to libvulkan [no]
 
 Toolchain options:
   --arch=ARCH              select architecture [$arch]
@@ -1987,6 +1988,7 @@ EXTERNAL_LIBRARY_LIST="
     openssl
     pocketsphinx
     vapoursynth
+    vulkan_static
 "
 
 HWACCEL_AUTODETECT_LIBRARY_LIST="
@@ -7379,7 +7381,10 @@ enabled vdpau &&
 enabled vdpau &&
     check_lib vdpau_x11 "vdpau/vdpau.h vdpau/vdpau_x11.h" vdp_device_create_x11 -lvdpau -lX11
 
-if enabled vulkan; then
+if enabled_all vulkan vulkan_static; then
+    check_pkg_config vulkan "vulkan >= 1.3.277" "vulkan/vulkan.h" "defined VK_VERSION_1_3" ||
+        check_lib vulkan "vulkan/vulkan.h" vkGetInstanceProcAddr -lvulkan
+elif enabled vulkan; then
     check_pkg_config_header_only vulkan "vulkan >= 1.3.277" "vulkan/vulkan.h" "defined VK_VERSION_1_3" ||
         check_cpp_condition vulkan "vulkan/vulkan.h" "defined(VK_VERSION_1_4) || (defined(VK_VERSION_1_3) && VK_HEADER_VERSION >= 277)"
 fi

libavutil/hwcontext_vulkan.c

@@ -533,11 +533,19 @@ static int vkfmt_from_pixfmt2(AVHWDeviceContext *dev_ctx, enum AVPixelFormat p,
     return AVERROR(EINVAL);
 }
 
+#if CONFIG_VULKAN_STATIC
+VKAPI_ATTR PFN_vkVoidFunction VKAPI_CALL vkGetInstanceProcAddr(VkInstance instance,
+                                                               const char *pName);
+#endif
+
 static int load_libvulkan(AVHWDeviceContext *ctx)
 {
     VulkanDevicePriv *p = ctx->hwctx;
     AVVulkanDeviceContext *hwctx = &p->p;
 
+#if CONFIG_VULKAN_STATIC
+    hwctx->get_proc_addr = vkGetInstanceProcAddr;
+#else
     static const char *lib_names[] = {
 #if defined(_WIN32)
         "vulkan-1.dll",
@@ -563,6 +571,7 @@ static int load_libvulkan(AVHWDeviceContext *ctx)
     }
 
     hwctx->get_proc_addr = (PFN_vkGetInstanceProcAddr)dlsym(p->libvulkan, "vkGetInstanceProcAddr");
+#endif /* CONFIG_VULKAN_STATIC */
 
     return 0;
 }