Build the C part as a separate convenience library

src/Makefile.am

@@ -2,32 +2,37 @@
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
+noinst_LTLIBRARIES = libmtime_c.la
+
 lib_LTLIBRARIES = libmtime.la
+libmtime_la_LIBADD = libmtime_c.la
 
 AM_CPPFLAGS = -I$(top_srcdir)/include
 
-libmtime_la_SOURCES =         \
-    kepler.c                  \
-    libmtime.f90              \
-    mtime_c_bindings.f90      \
-    mtime_calendar.c          \
-    mtime_calendar360day.c    \
-    mtime_calendar365day.c    \
+libmtime_c_la_SOURCES = \
+    kepler.c \
+    mtime_calendar.c \
+    mtime_calendar360day.c \
+    mtime_calendar365day.c \
     mtime_calendarGregorian.c \
-    mtime_constants.f90       \
-    mtime_date.c              \
-    mtime_datetime.c          \
-    mtime_error_handling.f90  \
-    mtime_eventHandling.c     \
-    mtime_eventList.c         \
-    mtime_iso8601.c           \
-    mtime_julianDay.c         \
-    mtime_time.c              \
-    mtime_timedelta.c         \
-    mtime_utilities.c         \
-    orbit.c                   \
+    mtime_date.c \
+    mtime_datetime.c \
+    mtime_eventHandling.c \
+    mtime_eventList.c \
+    mtime_iso8601.c \
+    mtime_julianDay.c \
+    mtime_time.c \
+    mtime_timedelta.c \
+    mtime_utilities.c \
+    orbit.c \
     vsop87.c
 
+libmtime_la_SOURCES = \
+    libmtime.f90 \
+    mtime_c_bindings.f90 \
+    mtime_constants.f90 \
+    mtime_error_handling.f90
+
 if ENABLE_FORTRAN_HL
 libmtime_la_SOURCES += \
     libmtime_hl.f90 \