sci-ml/pytorch: apply mimalloc patch from caffe2

Closes: https://bugs.gentoo.org/980675
Signed-off-by: Alfredo Tupone <tupone@gentoo.org>

sci-ml/pytorch/files/pytorch-2.13.0-mimalloc.patch

@@ -0,0 +1,24 @@
+--- a/c10/CMakeLists.txt	2026-02-01 09:22:55.398151644 +0100
++++ b/c10/CMakeLists.txt	2026-02-01 09:30:46.720495230 +0100
+@@ -120,8 +120,9 @@
+   endif()
+ 
+   if(USE_MIMALLOC)
+-    target_link_libraries(c10 PRIVATE "mimalloc-static")
+-    add_dependencies(c10 mimalloc-static)
++    find_package(mimalloc REQUIRED)
++    target_link_libraries(c10 PRIVATE "mimalloc")
++    add_dependencies(c10 mimalloc)
+   endif()
+ 
+   if(LINUX)
+--- a/CMakeLists.txt	2026-02-03 16:47:46.949580063 +0100
++++ b/CMakeLists.txt	2026-02-03 16:48:57.348716061 +0100
+@@ -404,7 +404,6 @@
+ # on Windows and AArch64.
+ option(USE_MIMALLOC_ON_MKL "Use mimalloc on MKL" OFF)
+ if(WIN32 OR (CPU_AARCH64 AND NOT APPLE))
+-  set(USE_MIMALLOC ON)
+   # Disable OPT flags for mimalloc on aarch64 as it breaks ARMv8.0
+   # Not enable USE_MIMALLOC_ON_MKL due to it caused issue:
+   # See https://github.com/pytorch/pytorch/issues/174344

sci-ml/pytorch/pytorch-2.13.0-r3.ebuild

@@ -163,6 +163,7 @@ BDEPEND="dev-build/cmake"
 PATCHES=(
 	"${FILESDIR}"/${P}-aotriton-fixes.patch
 	"${FILESDIR}"/${P}-glog.patch
+	"${FILESDIR}"/${P}-mimalloc.patch
 	"${FILESDIR}"/${P}-removekineto-pr178960.patch
 	"${FILESDIR}"/${P}-rocm-assert-fix.patch
 	"${FILESDIR}"/${P}-unbundle_fbgemm.patch