pidgin/pidgin

Use LT_LIB_M to determine if we need to link to the math library and link Pidgin to the X11 libraries
release-2.x.y
2021-04-11, Gary Kramlich
132d17234930
Use LT_LIB_M to determine if we need to link to the math library and link Pidgin to the X11 libraries

Gentoo ran into an issue with the gold linker without -lm. The original patch
and work came from Justin Lechner. https://bugs.gentoo.org/386079

Gentoo also ran into an issue with X11_LIBS not being added to pidgin. This
should already be implicit everywhere except for homebrew which patches X11
out of their build. Original patch/work came from and. https://bugs.gentoo.org/500762

Testing Done:
Installed and ran locally.

Reviewed at https://reviews.imfreedom.org/r/608/
plugindir = $(libdir)/pidgin
gestures_la_LDFLAGS = -module -avoid-version
if PLUGINS
plugin_LTLIBRARIES = gestures.la
gestures_la_SOURCES = \
gestures.c \
gstroke.h \
gstroke-internal.h \
stroke.c \
stroke-draw.c
gestures_la_LIBADD = $(GTK_LIBS)
endif
AM_CPPFLAGS = \
-DDATADIR=\"$(datadir)\" \
-I$(top_srcdir)/libpurple \
-I$(top_builddir)/libpurple \
-I$(top_srcdir)/pidgin \
$(DEBUG_CFLAGS) \
$(GTK_CFLAGS)