Add force_dynamic_crt to build as static library but with /MD on windows

gypfiles/toolchain.gypi

Index: gypfiles/toolchain.gypi
diff --git a/gypfiles/toolchain.gypi b/gypfiles/toolchain.gypi
index a85c6607d0aeb73c7c8ff2be27814b406ca3507a..4778b110614496aee8935c131141dd37b447a160 100644
--- a/gypfiles/toolchain.gypi
+++ b/gypfiles/toolchain.gypi
@@ -41,6 +41,7 @@
     'coverage%': 0,
     'v8_target_arch%': '<(target_arch)',
     'v8_host_byteorder%': '<!(python -c "import sys; print sys.byteorder")',
+    'force_dynamic_crt%': 0,
     # Native Client builds currently use the V8 ARM JIT and
     # arm/simulator-arm.cc to defer the significant effort required
     # for NaCl JIT support. The nacl_target_arch variable provides
@@ -1110,7 +1111,7 @@
           'VCCLCompilerTool': {
             'Optimization': '0',
             'conditions': [
-              ['component=="shared_library"', {
+              ['component=="shared_library" or force_dynamic_crt==1', {
                 'RuntimeLibrary': '3',  # /MDd
               }, {
                 'RuntimeLibrary': '1',  # /MTd
@@ -1162,7 +1163,7 @@
             'StringPooling': 'true',
             'BasicRuntimeChecks': '0',
             'conditions': [
-              ['component=="shared_library"', {
+              ['component=="shared_library" or force_dynamic_crt==1', {
                 'RuntimeLibrary': '3',  #/MDd
               }, {
                 'RuntimeLibrary': '1',  #/MTd
@@ -1353,7 +1354,7 @@
                 'FavorSizeOrSpeed': '0',
                 'StringPooling': 'true',
                 'conditions': [
-                  ['component=="shared_library"', {
+                  ['component=="shared_library" or force_dynamic_crt==1', {
                     'RuntimeLibrary': '2',  #/MD
                   }, {
                     'RuntimeLibrary': '0',  #/MT