libeatmydata: fix build on musl

srcpkgs/libeatmydata/patches/musl.patch

@@ -0,0 +1,18 @@
+In musl open64 is by default a #define to open.
+However, it provides compat symbols and we want this
+to explicitly use those.
+
+--- libeatmydata/libeatmydata.c
++++ libeatmydata/libeatmydata.c
+@@ -27,6 +27,11 @@
+ #include <stdarg.h>
+ #include <pthread.h>
+ 
++/* refer to the compat alias in musl */
++#if !defined(__GLIBC__)
++#undef open64
++#endif
++
+ /* 
+ #define CHECK_FILE "/tmp/eatmydata"
+ */