[mono-runtimes] Disable mono's IL interpreter (#1010)

Context: mono/mono#5925

Mono's IL interpreter will be enabled by default in mono once the
above PR merged. Xamarin.Android doesn't need an IL interpreter --
we have a JIT! -- so disable the interpreter so that it doesn't
impact the size of `libmonosgen-2.0.so`.

Author: lewurm

build-tools/mono-runtimes/mono-runtimes.props

@@ -7,7 +7,7 @@
     <_HostWinCFlags Condition=" '$(Configuration)' == 'Release' ">-g -O2 -DXAMARIN_PRODUCT_VERSION=0</_HostWinCFlags>
     <_BtlsConfigureFlags>--enable-dynamic-btls --with-btls-android-ndk=$(AndroidToolchainDirectory)\ndk</_BtlsConfigureFlags>
     <_CommonConfigureFlags>--without-ikvm-native --enable-maintainer-mode --with-profile4_x=no --with-monodroid --enable-nls=no --with-sigaltstack=yes --with-tls=pthread mono_cv_uscore=yes</_CommonConfigureFlags>
-    <_TargetConfigureFlags>$(_CommonConfigureFlags) --enable-minimal=ssa,portability,attach,verifier,full_messages,sgen_remset,sgen_marksweep_par,sgen_marksweep_fixed,sgen_marksweep_fixed_par,sgen_copying,logging,security,shared_handles --disable-mcs-build --disable-executables --disable-iconv --disable-boehm $(_BtlsConfigureFlags)</_TargetConfigureFlags>
+    <_TargetConfigureFlags>$(_CommonConfigureFlags) --enable-minimal=ssa,interpreter,portability,attach,verifier,full_messages,sgen_remset,sgen_marksweep_par,sgen_marksweep_fixed,sgen_marksweep_fixed_par,sgen_copying,logging,security,shared_handles --disable-mcs-build --disable-executables --disable-iconv --disable-boehm $(_BtlsConfigureFlags)</_TargetConfigureFlags>
     <_SecurityCFlags>-fstack-protector</_SecurityCFlags>
     <_TargetCFlags>$(_SecurityCFlags) -DMONODROID=1</_TargetCFlags>
     <_TargetCxxFlags>$(_SecurityCFlags) -DMONODROID=1</_TargetCxxFlags>