gnu: OpenColorIO: Fix build with GCC 11.

* gnu/packages/patches/opencolorio-fix-build-with-gcc11.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/image-processing.scm (opencolorio)[source]: Use it.

gnu/local.mk

@@ -1626,6 +1626,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/openboardview-use-system-imgui.patch	\
   %D%/packages/patches/openboardview-use-system-mpc.patch	\
   %D%/packages/patches/openbox-python3.patch			\
+  %D%/packages/patches/opencolorio-fix-build-with-gcc11.patch	\
   %D%/packages/patches/openfoam-4.1-cleanup.patch			\
   %D%/packages/patches/openjdk-9-pointer-comparison.patch       \
   %D%/packages/patches/openjdk-9-setsignalhandler.patch         \

gnu/packages/image-processing.scm

@@ -262,6 +262,7 @@ of external libraries that provide additional functionality.")
        (uri (git-reference
              (url "https://github.com/AcademySoftwareFoundation/OpenColorIO")
              (commit (string-append "v" version))))
+       (patches (search-patches "opencolorio-fix-build-with-gcc11.patch"))
        (sha256
         (base32 "12srvxca51czpfjl0gabpidj9n84mw78ivxy5w75qhq2mmc798sb"))
        (file-name (git-file-name name version))

gnu/packages/patches/opencolorio-fix-build-with-gcc11.patch

@@ -0,0 +1,37 @@
+Fix build failure with GCC 11:
+
+------
+[...]
+/tmp/guix-build-opencolorio-1.1.1.drv-0/source/src/core/ImageDesc.cpp:60:51: error: ‘this’ pointer is null [-Werror=nonnull]
+   60 |             os << "width=" << packedImg->getWidth() << ", ";
+      |                                                   ^
+/tmp/guix-build-opencolorio-1.1.1.drv-0/source/src/core/ImageDesc.cpp:274:10: note: in a call to non-static member function ‘long int OpenColorIO::v1::PackedImageDesc::getWidth() const’
+  274 |     long PackedImageDesc::getWidth() const
+      |          ^~~~~~~~~~~~~~~
+/tmp/guix-build-opencolorio-1.1.1.drv-0/source/src/core/ImageDesc.cpp:61:53: error: ‘this’ pointer is null [-Werror=nonnull]
+   61 |             os << "height=" << packedImg->getHeight() << ", ";
+      |                                                     ^
+/tmp/guix-build-opencolorio-1.1.1.drv-0/source/src/core/ImageDesc.cpp:279:10: note: in a call to non-static member function ‘long int OpenColorIO::v1::PackedImageDesc::getHeight() const’
+  279 |     long PackedImageDesc::getHeight() const
+      |          ^~~~~~~~~~~~~~~
+cc1plus: all warnings being treated as errors
+[...]
+------
+
+Patch copied from Gentoo:
+
+https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=7e726d850502018b6760da78dbd4a419603016b8
+
+diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
+index 1eb691b6..cff9bd83 100644
+--- a/src/core/CMakeLists.txt
++++ b/src/core/CMakeLists.txt
+@@ -23,8 +23,6 @@ if(WIN32)
+     if("${CMAKE_BUILD_TYPE}" STREQUAL "Release")
+         set(EXTERNAL_COMPILE_FLAGS "${EXTERNAL_COMPILE_FLAGS} /WX")
+     endif()
+-else()
+-    set(EXTERNAL_COMPILE_FLAGS "${EXTERNAL_COMPILE_FLAGS} -Werror")
+ endif()
+ 
+ # SHARED