[build] Added runtime/_tmpinst/mcs script to unbreak system.web tests for 2.0

Also made gmcs force -sdk=2 since -sdk=4 is now the default. _tmpinst/mcs is needed because
the CSharp CodeDOM provider invokes it and without the script in place it will launch the
first mcs available in the path.

runtime/Makefile.am

@@ -100,7 +100,7 @@ clean-local:
 
 endif BUILD_MCS
 
-TEST_SUPPORT_FILES = $(tmpinst)/bin/mono $(tmpinst)/bin/ilasm $(tmpinst)/bin/gmcs $(tmpinst)/bin/dmcs $(tmpinst)/bin/al2 $(tmpinst)/bin/al
+TEST_SUPPORT_FILES = $(tmpinst)/bin/mono $(tmpinst)/bin/ilasm $(tmpinst)/bin/mcs $(tmpinst)/bin/gmcs $(tmpinst)/bin/dmcs $(tmpinst)/bin/al2 $(tmpinst)/bin/al
 
 # now a misnomer, but it'll go away soon enough.
 if ENABLE_NUNIT_TESTS
@@ -172,12 +172,18 @@ $(tmpinst)/bin/mono: mono-wrapper etc/mono/config
 	$(mkinstalldirs) $(tmpinst)/bin
 	cp mono-wrapper $@
 
-$(tmpinst)/bin/gmcs: $(tmpinst)/bin/mono Makefile
+$(tmpinst)/bin/mcs: $(tmpinst)/bin/mono Makefile
 	echo '#! /bin/sh' > $@ ; \
 	r=`pwd`; m=`cd $(mcs_topdir) && pwd`; \
 	echo 'exec "'"$$r/$(tmpinst)/bin/mono"'" "'"$$m/class/lib/basic/mcs.exe"'" "$$@"' >> $@ ; \
 	chmod +x $@
 
+$(tmpinst)/bin/gmcs: $(tmpinst)/bin/mono Makefile
+	echo '#! /bin/sh' > $@ ; \
+	r=`pwd`; m=`cd $(mcs_topdir) && pwd`; \
+	echo 'exec "'"$$r/$(tmpinst)/bin/mono"'" "'"$$m/class/lib/basic/mcs.exe -sdk:2"'" "$$@"' >> $@ ; \
+	chmod +x $@
+
 $(tmpinst)/bin/dmcs: $(tmpinst)/bin/mono Makefile
 	echo '#! /bin/sh' > $@ ; \
 	r=`pwd`; m=`cd $(mcs_topdir) && pwd`; \