more robust options;

--- a/src/Pure/Admin/build_polyml.scala	Sun Feb 11 13:24:38 2018 +0100
+++ b/src/Pure/Admin/build_polyml.scala	Sun Feb 11 13:45:51 2018 +0100
@@ -22,31 +22,29 @@
       Platform_Info(
         options_multilib =
           List("--build=i386", "CFLAGS=-m32 -O3", "CXXFLAGS=-m32 -O3", "CCASFLAGS=-m32",
-            "LDFLAGS=-Wl,-rpath,_DUMMY_"),
-        options = List("LDFLAGS=-Wl,-rpath,_DUMMY_")),
+            "LDFLAGS=-Wl,-rpath,_DUMMY_", "--enable-shared", "--without-gmp"),
+        options = List("LDFLAGS=-Wl,-rpath,_DUMMY_", "--enable-shared")),
     "x86_64-linux" ->
       Platform_Info(
-        options = List("LDFLAGS=-Wl,-rpath,_DUMMY_")),
+        options = List("LDFLAGS=-Wl,-rpath,_DUMMY_", "--enable-shared")),
     "x86-darwin" ->
       Platform_Info(
         options =
           List("--build=i686-darwin", "CFLAGS=-arch i686 -O3 -I../libffi/include",
             "CXXFLAGS=-arch i686 -O3 -I../libffi/include", "CCASFLAGS=-arch i686 -O3",
-            "LDFLAGS=-segprot POLY rwx rwx -L/usr/local/lib32",
-            "--disable-shared"),
+            "LDFLAGS=-segprot POLY rwx rwx -L/usr/local/lib32"),
         setup = "PATH=/usr/bin:/bin:/usr/sbin:/sbin"),
     "x86_64-darwin" ->
       Platform_Info(
         options =
           List("--build=x86_64-darwin", "CFLAGS=-arch x86_64 -O3 -I../libffi/include",
             "CXXFLAGS=-arch x86_64 -O3 -I../libffi/include", "CCASFLAGS=-arch x86_64",
-            "LDFLAGS=-segprot POLY rwx rwx"),
+            "LDFLAGS=-segprot POLY rwx rwx", "--enable-shared"),
         setup = "PATH=/usr/bin:/bin:/usr/sbin:/sbin"),
     "x86-windows" ->
       Platform_Info(
         options =
-          List("--host=i686-w32-mingw32", "CPPFLAGS=-I/mingw32/include",
-            "--disable-windows-gui", "--disable-shared"),
+          List("--host=i686-w32-mingw32", "CPPFLAGS=-I/mingw32/include", "--disable-windows-gui"),
         setup =
           """PATH=/usr/bin:/bin:/mingw32/bin
             export CONFIG_SITE=/etc/config.site""",
@@ -57,8 +55,7 @@
     "x86_64-windows" ->
       Platform_Info(
         options =
-          List("--host=x86_64-w64-mingw32", "CPPFLAGS=-I/mingw64/include",
-            "--disable-windows-gui", "--disable-shared"),
+          List("--host=x86_64-w64-mingw32", "CPPFLAGS=-I/mingw64/include", "--disable-windows-gui"),
         setup =
           """PATH=/usr/bin:/bin:/mingw64/bin
             export CONFIG_SITE=/etc/config.site""",
@@ -113,7 +110,7 @@
     /* configure and make */
 
     val configure_options =
-      List("--enable-shared", "--enable-intinf-as-int", "--with-gmp") :::
+      List("--enable-intinf-as-int", "--with-gmp") :::
       (if (!arch_64 && Isabelle_System.getenv("ISABELLE_PLATFORM64") == "x86_64-linux")
         info.options_multilib
        else info.options) ::: options