build: drop diff.exe from windows builds

The shipped versions of xdiff already does everything diff does, so this
duplication of tools isn't necessary. Furthermore, this setup is more
consistent overall, as the 'diffopt=external' option should be for
external programs rather than programs we bundle neovim with.

Install diffutils for oldtests in CI to avoid needing to modify tests.

.github/workflows/test.yml

@@ -354,7 +354,7 @@ jobs:
         with:
           update: true
           pacboy: >-
-            make:p gcc:p
+            make:p gcc:p diffutils:p
           release: false
 
       - if: success() || failure() && steps.abort_job.outputs.status == 'success'

cmake.deps/CMakeLists.txt

@@ -164,11 +164,9 @@ set(LUV_SHA256 222b38b6425f0926218e14e7da81481fdde6f9660c1feac25a53e6fb52e886e6)
 set(LUA_COMPAT53_URL https://github.com/keplerproject/lua-compat-5.3/archive/v0.9.tar.gz)
 set(LUA_COMPAT53_SHA256 ad05540d2d96a48725bb79a1def35cf6652a4e2ec26376e2617c8ce2baa6f416)
 
-# Windows only: cat.exe diff.exe tee.exe xxd.exe
+# Windows only: cat.exe tee.exe xxd.exe
 set(CAT_URL https://github.com/neovim/deps/raw/21c5e8bdda33521a6ed497b315e03265a2785cbc/opt/cat.exe)
 set(CAT_SHA256 93b8d307bb15af3968920bdea3beb869a49d166f9164853c58a4e6ffdcae61c6)
-set(DIFF_URL https://github.com/neovim/deps/raw/21c5e8bdda33521a6ed497b315e03265a2785cbc/opt/diff.exe)
-set(DIFF_SHA256 4ceceebc8150422c6d8d9a06c2e9686d5a5d90f1033f60ad92ab81fe810e2a28)
 set(TEE_URL https://github.com/neovim/deps/raw/21c5e8bdda33521a6ed497b315e03265a2785cbc/opt/tee.exe)
 set(TEE_SHA256 950eea4e17fa3a7e89fa2c55374037b5797b3f1a54fea1304634884ab42ec14d)
 set(XXD_URL https://github.com/neovim/deps/raw/21c5e8bdda33521a6ed497b315e03265a2785cbc/opt/xxd.exe)
@@ -267,7 +265,6 @@ if(WIN32)
   include(GetBinaryDeps)
 
   GetExecutable(TARGET cat)
-  GetExecutable(TARGET diff)
   GetExecutable(TARGET tee)
   GetExecutable(TARGET xxd)
 

src/nvim/CMakeLists.txt

@@ -762,7 +762,6 @@ if(WIN32)
     "file(MAKE_DIRECTORY \"${PROJECT_BINARY_DIR}/windows_runtime_deps/platforms\")")
   foreach(DEP_FILE IN ITEMS
       cat.exe
-      diff.exe
       tee.exe
       win32yank.exe
       xxd.exe