Sorry, but I can't seem to apply git diff. I tried editing the
Makefile manually (it's just the line "$(call inc_path,lcms2) \",
right?) but then I can't apply the patch. I get stuck here:

$ git am /home/paz/patch/*.patch
Starting: add lcms2 2.13.1 for ffmpeg 5.1
error: cinelerra-5.1/thirdparty/Makefile: non corrisponde all'indice
Patch non riuscita a 0001 add lcms2 2.13.1 for ffmpeg 5.1
suggerimento: Usa 'git am --show-current-patch=diff' per visualizzare
la patch non riuscita
Una volta risolto questo problema, esegui "git am --continue".
Se preferisci saltare questa patch, esegui invece "git am --skip".
Per ripristinare il branch originario e terminare il patching, esegui
"git am --abort".

[paz@arch-paz cinelerra-5.1]$ git am --show-current-patch=diff
---
 cinelerra-5.1/configure.ac        |  6 ++++++
 cinelerra-5.1/thirdparty/Makefile | 11 +++++++++--
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/cinelerra-5.1/configure.ac b/cinelerra-5.1/configure.ac
index ab06ace9..06c0531d 100644
--- a/cinelerra-5.1/configure.ac
+++ b/cinelerra-5.1/configure.ac
@@ -494,6 +494,11 @@ PKG_3RD([libbthread],[auto],
   [ . ])
 fi

+PKG_3RD([lcms2],[auto],
+  [lcms2-2.13.1],
+  [ src/.libs/liblcms2.a ],
+  [ include ])
+

 AC_SUBST(STATIC_PKGS)

@@ -1042,6 +1047,7 @@ PKG_PROVIDE([sord], [$WANT_LV2])
 PKG_PROVIDE([suil], [$WANT_LV2])
 PKG_PROVIDE([ffnvcodec], [$WANT_NV])
 PKG_PROVIDE([libdpx])
+PKG_PROVIDE([lcms2])
:

>> libtoolize: Consider adding 'AC_CONFIG_MACRO_DIRS([m4])' to configure.ac,
>> libtoolize: and rerunning libtoolize and aclocal.
> What will happen if you follow this suggestion?
By making the recommended corrections the warning no longer appears,
everything works fine with or without corrections.