PostgreSQL cannot be compiled on RISC-V

The full log is here:
https://fedorapeople.org/groups/risc-v/logs/postgresql/9.5.5-1.fc25.0.riscv64/build.log

The extract which fails is:

gcc -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Wendif-labels -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv -fexcess-precision=standard -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -DLINUX_OOM_SCORE_ADJ=0 -fpic -I. -I. -I/usr/include/python3.5m -I../../../src/include -D_GNU_SOURCE -I/usr/include/libxml2 -c -o plpy_cursorobject.o plpy_cursorobject.c
In file included from ../../../src/include/storage/lwlock.h:18:0,
from ../../../src/include/storage/lock.h:18,
from ../../../src/include/access/genam.h:20,
from ../../../src/include/nodes/execnodes.h:17,
from ../../../src/include/executor/execdesc.h:18,
from ../../../src/include/utils/portal.h:50,
from ../../../src/include/executor/spi.h:18,
from plpy_planobject.h:8,
from plpy_cursorobject.c:18:
../../../src/include/storage/s_lock.h:890:2: error: #error PostgreSQL does not have native spinlock support on this platform. To continue the compilation, rerun configure using --disable-spinlocks. However, performance will be poor. Please report this to pgsql-bugs(at)postgresql(dot)org(dot)
#error PostgreSQL does not have native spinlock support on this platform. To continue the compilation, rerun configure using --disable-spinlocks. However, performance will be poor. Please report this to pgsql-bugs(at)postgresql(dot)org(dot)
^~~~~
../../../src/include/storage/s_lock.h:962:25: error: unknown type name 'slock_t'
extern int tas(volatile slock_t *lock); /* in port/.../tas.s, or
^~~~~~~
../../../src/include/storage/s_lock.h:972:8: error: unknown type name 'slock_t'
extern slock_t dummy_spinlock;
^~~~~~~
../../../src/include/storage/s_lock.h:977:28: error: unknown type name 'slock_t'
extern int s_lock(volatile slock_t *lock, const char *file, int line);
^~~~~~~
In file included from ../../../src/include/storage/lock.h:18:0,
from ../../../src/include/access/genam.h:20,
from ../../../src/include/nodes/execnodes.h:17,
from ../../../src/include/executor/execdesc.h:18,
from ../../../src/include/utils/portal.h:50,
from ../../../src/include/executor/spi.h:18,
from plpy_planobject.h:8,
from plpy_cursorobject.c:18:
../../../src/include/storage/lwlock.h:50:2: error: unknown type name 'slock_t'
slock_t mutex; /* Protects LWLock and queue of PGPROCs */
^~~~~~~
<builtin>: recipe for target 'plpy_cursorobject.o' failed
make: *** [plpy_cursorobject.o] Error 1
error: Bad exit status from /var/tmp/rpm-tmp.ZVdDip (%build)

--
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