Link against math libraries when needed

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

Index: b/cgi-fcgi/Makefile.am
===================================================================
--- a/cgi-fcgi/Makefile.am
+++ b/cgi-fcgi/Makefile.am
@@ -11,5 +11,5 @@
 LIBDIR      = ../libfcgi
 LIBFCGI     = $(LIBDIR)/libfcgi.la
 
-LDADD = $(LIBFCGI)
+LDADD = $(LIBFCGI) -lm
 cgi_fcgi_SOURCES = $(INCLUDE_FILES) cgi-fcgi.c
Index: b/examples/Makefile.am
===================================================================
--- a/examples/Makefile.am
+++ b/examples/Makefile.am
@@ -21,7 +21,7 @@
 LIBDIR      = ../libfcgi
 LIBFCGI     = $(LIBDIR)/libfcgi.la
 
-LDADD = $(LIBFCGI)
+LDADD = $(LIBFCGI) -lm
 
 echo_SOURCES       = $(INCLUDE_FILES) echo.c
 echo_x_SOURCES     = $(INCLUDE_FILES) echo-x.c