gnu: qtbase: Always find libvulkan.

Fixes: guix/guix#3330

* gnu/packages/qt.scm (qtbase)[source]: Add patch.
[arguments]: Adjust a phase to substitute the location for libvulkan.so.
* gnu/packages/patches/qtbase-patch-libvulkan.patch: New file.
* gnu/local.mk (dist_patch_DATA): Register it.

Co-authored-by: kestrelwx <kestrel.w@proton.me>
Change-Id: I39f1be5a30c5c17a4e4ea6c853b475f20ba8272c
Signed-off-by: Andreas Enge <andreas@enge.fr>

1 files changed, 28 insertions, 0 deletions

diff --git a/gnu/packages/patches/qtbase-patch-libvulkan.patch b/gnu/packages/patches/qtbase-patch-libvulkan.patch
new file mode 100644
index 00000000000..b8b3847504e
--- /dev/null
+++ b/gnu/packages/patches/qtbase-patch-libvulkan.patch
@@ -0,0 +1,28 @@
+Add the full name for libvulkan.so.1 so that we can patch it in the 'build phase.
+Not sent upstream.
+
+diff --git a/src/gui/vulkan/qbasicvulkanplatforminstance.cpp b/src/gui/vulkan/qbasicvulkanplatforminstance.cpp
+index 47d9a7e9..80c929e5 100644
+--- a/src/gui/vulkan/qbasicvulkanplatforminstance.cpp
++++ b/src/gui/vulkan/qbasicvulkanplatforminstance.cpp
+@@ -45,7 +45,7 @@ QBasicPlatformVulkanInstance::~QBasicPlatformVulkanInstance()
+ 
+ void QBasicPlatformVulkanInstance::loadVulkanLibrary(const QString &defaultLibraryName, int defaultLibraryVersion)
+ {
+-    QVarLengthArray<std::pair<QString, int>, 3> loadList;
++    QVarLengthArray<std::pair<QString, int>, 4> loadList;
+ 
+     // First in the list of libraries to try is the manual override, relevant on
+     // embedded systems without a Vulkan loader and possibly with custom vendor
+@@ -63,6 +63,11 @@ void QBasicPlatformVulkanInstance::loadVulkanLibrary(const QString &defaultLibra
+     if (defaultLibraryVersion >= 0)
+         loadList.append({ defaultLibraryName, -1 });
+ 
++#ifdef __linux__
++    // As a fallback we append to the list the full default name of libvulkan.
++    loadList.append({ QString::fromUtf8("libvulkan.so.1"), -1 });
++#endif
++
+     bool ok = false;
+     for (const auto &lib : loadList) {
+         m_vulkanLib.reset(new QLibrary);