transmission: fix patch after convert to -Np1

patch(1) will apply -p1 to '^diff ' line to figure out the target
filename.

Fix: void-linux/void-packages#31646

void-linux/void-packages@5d7ce72

srcpkgs/transmission/patches/add-missing-files.patch

@@ -1,4 +1,4 @@
-diff --git libtransmission/subprocess-test.cmd libtransmission/subprocess-test.cmd
+diff --git a/libtransmission/subprocess-test.cmd b/libtransmission/subprocess-test.cmd
 new file mode 100644
 index 0000000..4d08d06
 --- /dev/null
@@ -52,7 +52,7 @@ index 0000000..4d08d06
 +:finish
 +    >nul move /y "%temp_result_path%" "%result_path%"
 +    exit /b 0
-diff --git po/pt_PT.po po/pt_PT.po
+diff --git a/po/pt_PT.po b/po/pt_PT.po
 new file mode 100644
 index 0000000..d9346f8
 --- /dev/null