[coretext] Use fabsf() instead of abs()

Fixes bots.

Link libharfbuzz.so with -lm.  Surprising that we survived without
it so far!

src/Makefile.am

@@ -122,7 +122,7 @@ endif
 
 libharfbuzz_la_SOURCES = $(HBSOURCES) $(HBHEADERS) $(HBNODISTHEADERS)
 libharfbuzz_la_CPPFLAGS = $(HBCFLAGS)
-libharfbuzz_la_LDFLAGS = $(AM_LDFLAGS) -version-info $(HB_LIBTOOL_VERSION_INFO) $(export_symbols) -no-undefined
+libharfbuzz_la_LDFLAGS = $(AM_LDFLAGS) -lm -version-info $(HB_LIBTOOL_VERSION_INFO) $(export_symbols) -no-undefined
 libharfbuzz_la_LIBADD = $(HBLIBS)
 EXTRA_libharfbuzz_la_DEPENDENCIES = $(harfbuzz_def_dependency)
 pkginclude_HEADERS = $(HBHEADERS)

src/harfbuzz.pc.in

@@ -8,6 +8,6 @@ Description: HarfBuzz text shaping library
 Version: %VERSION%
 
 Libs: -L${libdir} -lharfbuzz
-Libs.private: %libs_private%
+Libs.private: -lm %libs_private%
 Requires.private: %requires_private%
 Cflags: -I${includedir}/harfbuzz

src/hb-coretext.cc

@@ -30,6 +30,7 @@
 #include "hb-shaper-impl-private.hh"
 
 #include "hb-coretext.h"
+#include <math.h>
 
 
 #ifndef HB_DEBUG_CORETEXT
@@ -79,8 +80,8 @@ hb_coretext_face_create (CGFontRef cg_font)
 
 HB_SHAPER_DATA_ENSURE_DEFINE(coretext, face)
 HB_SHAPER_DATA_ENSURE_DEFINE_WITH_CONDITION(coretext, font,
-                                            abs (CTFontGetSize((CTFontRef) data) -
-                                                 (font->ptem <= 0 ? HB_CORETEXT_DEFAULT_FONT_SIZE : font->ptem)) < 1)
+                                            fabsf (CTFontGetSize((CTFontRef) data) -
+                                                   (font->ptem <= 0 ? HB_CORETEXT_DEFAULT_FONT_SIZE : font->ptem)) <= .5)
 
 /*
  * shaper face data