gnu: postgresql-13: Fix building on riscv64-linux....* gnu/packages/databases.scm (postgresql-13)[arguments]: Add phase when
buidling for riscv64-linux to apply a patch.
[native-inputs]: When building for riscv64-linux add patch and patch
file.
* gnu/packages/patches/postgresql-riscv-spinlocks.patch: New file.
* gnu/local.mk (dist_patch_DATA): Register it.