also try to find the library without pkg-config

Author: dimpase

build/pkgs/sirocco/spkg-configure.m4

@@ -3,8 +3,28 @@ SAGE_SPKG_CONFIGURE([sirocco], [
   PKG_CHECK_MODULES([libsirocco], [libsirocco >= 2.1.0], [
     AC_MSG_RESULT([found libsirocco >= 2.1.0, will use installed version])
   ],[
-    AC_MSG_RESULT([couldn't find libsirocco >= 2.1.0. It will be installed])
-    sage_spkg_install_sirocco=yes
+    AC_MSG_RESULT([couldn't find libsirocco >= 2.1.0. Trying to find an instance without pkg-config])
+    AC_CHECK_HEADER([sirocco.h], [
+         BACKUP_LIBS=${LIBS}
+	 LIBS="${LIBS} -lmpfr -lsirocco"
+         AC_LINK_IFELSE([
+            AC_LANG_PROGRAM(
+            [[#include <sirocco.h>
+            ]], [[
+	      double tcoefs[]={-2.,2.};
+	      homotopyPath(2, tcoefs, 1., 0.);
+            ]])], [
+                AC_MSG_RESULT([yes])
+            ], [
+                AC_MSG_RESULT([no])
+                sage_spkg_install_sirocco=yes
+            ], [
+                dnl assume that the person running cross-compiling
+                dnl knows what they are doing
+                AC_MSG_RESULT([yes])
+            ]) 
+	 LIBS=${BACKUP_LIBS}
+  ], [sage_spkg_install_sirocco=yes])
   ])
  ])
 ])