drawterm: fix '^diff ' line in patches

patch(1) also applies -p1 to this line

srcpkgs/drawterm/patches/posix_generic.patch

@@ -15,7 +15,7 @@ Also make sure our CFLAGS/LDFLAGS are respected.
  create mode 100644 posix-generic/getcallerpc.c
  create mode 100644 posix-generic/tas.c
 
-diff --git Make.unix Make.unix
+diff --git a/Make.unix b/Make.unix
 index f61c516..3a536b3 100644
 --- a/Make.unix
 +++ b/Make.unix
@@ -45,7 +45,7 @@ index f61c516..3a536b3 100644
 -	arch=`uname -m|sed 's/i.86/386/;s/Power Macintosh/power/; s/x86_64/amd64/; s/armv[567].*/arm/; s/aarch64/arm64/'`; \
 -	(cd posix-$$arch &&  make)
 +	cd posix-generic && make
-diff --git posix-generic/Makefile posix-generic/Makefile
+diff --git a/posix-generic/Makefile b/posix-generic/Makefile
 new file mode 100644
 index 0000000..970204e
 --- /dev/null
@@ -66,7 +66,7 @@ index 0000000..970204e
 +
 +%.$O: %.c
 +	$(CC) $(CFLAGS) $*.c
-diff --git posix-generic/getcallerpc.c posix-generic/getcallerpc.c
+diff --git a/posix-generic/getcallerpc.c b/posix-generic/getcallerpc.c
 new file mode 100644
 index 0000000..3614c59
 --- /dev/null
@@ -80,7 +80,7 @@ index 0000000..3614c59
 +{
 +	return ((uintptr*)a)[-1];
 +}
-diff --git posix-generic/tas.c posix-generic/tas.c
+diff --git a/posix-generic/tas.c b/posix-generic/tas.c
 new file mode 100644
 index 0000000..289f747
 --- /dev/null