Add "-no-undefined" to linker flags of threading libraries to allow building
shared libraries on Windows.

diff -urN fftw-3.3.10/threads/Makefile.am.orig fftw-3.3.10/threads/Makefile.am
--- fftw-3.3.10/threads/Makefile.am.orig	2020-12-10 13:02:44.000000000 +0100
+++ fftw-3.3.10/threads/Makefile.am	2023-03-02 12:09:54.323824700 +0100
@@ -21,7 +21,9 @@
 threads.h dft-vrank-geq1.c ct.c rdft-vrank-geq1.c hc2hc.c		\
 vrank-geq1-rdft2.c f77api.c f77funcs.h
 libfftw3@PREC_SUFFIX@_threads_la_CFLAGS = $(AM_CFLAGS) $(PTHREAD_CFLAGS)
-libfftw3@PREC_SUFFIX@_threads_la_LDFLAGS = -version-info @SHARED_VERSION_INFO@
+libfftw3@PREC_SUFFIX@_threads_la_LDFLAGS = \
+@QUAD_FALSE@@COMBINED_THREADS_FALSE@  -no-undefined \
+  -version-info @SHARED_VERSION_INFO@
 if !COMBINED_THREADS
 libfftw3@PREC_SUFFIX@_threads_la_LIBADD = ../libfftw3@PREC_SUFFIX@.la
 endif
@@ -30,7 +32,9 @@
 threads.h dft-vrank-geq1.c ct.c rdft-vrank-geq1.c hc2hc.c	\
 vrank-geq1-rdft2.c f77api.c f77funcs.h
 libfftw3@PREC_SUFFIX@_omp_la_CFLAGS = $(AM_CFLAGS) $(OPENMP_CFLAGS)
-libfftw3@PREC_SUFFIX@_omp_la_LDFLAGS = -version-info @SHARED_VERSION_INFO@
+libfftw3@PREC_SUFFIX@_omp_la_LDFLAGS = \
+@QUAD_FALSE@@COMBINED_THREADS_FALSE@  -no-undefined \
+  -version-info @SHARED_VERSION_INFO@
 if !COMBINED_THREADS
 libfftw3@PREC_SUFFIX@_omp_la_LIBADD = ../libfftw3@PREC_SUFFIX@.la
 endif
diff -urN fftw-3.3.10/threads/Makefile.in.orig fftw-3.3.10/threads/Makefile.in
--- fftw-3.3.10/threads/Makefile.in.orig	2021-09-14 16:43:46.000000000 +0200
+++ fftw-3.3.10/threads/Makefile.in	2023-03-02 12:12:36.736513100 +0100
@@ -414,14 +414,18 @@
 vrank-geq1-rdft2.c f77api.c f77funcs.h
 
 libfftw3@PREC_SUFFIX@_threads_la_CFLAGS = $(AM_CFLAGS) $(PTHREAD_CFLAGS)
-libfftw3@PREC_SUFFIX@_threads_la_LDFLAGS = -version-info @SHARED_VERSION_INFO@
+libfftw3@PREC_SUFFIX@_threads_la_LDFLAGS = \
+@QUAD_FALSE@@COMBINED_THREADS_FALSE@  -no-undefined \
+  -version-info @SHARED_VERSION_INFO@
 @COMBINED_THREADS_FALSE@libfftw3@PREC_SUFFIX@_threads_la_LIBADD = ../libfftw3@PREC_SUFFIX@.la
 libfftw3@PREC_SUFFIX@_omp_la_SOURCES = api.c conf.c openmp.c	\
 threads.h dft-vrank-geq1.c ct.c rdft-vrank-geq1.c hc2hc.c	\
 vrank-geq1-rdft2.c f77api.c f77funcs.h
 
 libfftw3@PREC_SUFFIX@_omp_la_CFLAGS = $(AM_CFLAGS) $(OPENMP_CFLAGS)
-libfftw3@PREC_SUFFIX@_omp_la_LDFLAGS = -version-info @SHARED_VERSION_INFO@
+libfftw3@PREC_SUFFIX@_omp_la_LDFLAGS = \
+@QUAD_FALSE@@COMBINED_THREADS_FALSE@  -no-undefined \
+  -version-info @SHARED_VERSION_INFO@
 @COMBINED_THREADS_FALSE@libfftw3@PREC_SUFFIX@_omp_la_LIBADD = ../libfftw3@PREC_SUFFIX@.la
 all: all-am
 
