Test on/off CRT static

Author: alexcrichton

.appveyor.yml

@@ -1,6 +1,9 @@
 environment:
   matrix:
   - TARGET: x86_64-pc-windows-msvc
+    RUSTFLAGS: -C target-feature=-crt-static
+  - TARGET: x86_64-pc-windows-msvc
+    RUSTFLAGS: -C target-feature=+crt-static
   - TARGET: i686-pc-windows-msvc
   - TARGET: i686-pc-windows-gnu
     MSYS_BITS: 32

src/lib.rs

@@ -72,7 +72,6 @@ impl Build {
         configure
             // No shared objects, we just want static libraries
             .arg("no-dso")
-            .arg("no-shared")
 
             // Should be off by default on OpenSSL 1.1.0, but let's be extra sure
             .arg("no-ssl3")
@@ -97,11 +96,20 @@ impl Build {
             // On MSVC we need nasm.exe to compile the assembly files, but let's
             // just pessimistically assume for now that's not available.
             configure.arg("no-asm");
+
+            let features = env::var("CARGO_CFG_TARGET_FEATURE")
+                      .unwrap_or(String::new());
+            if features.contains("crt-static") {
+                configure.arg("no-shared");
+            }
         } else {
             // If we're *not* on MSVC then we can optimize our build a bit by
             // avoiding building the CLI tools. Unfortunately though on MSVC if
             // we pass this option the build breaks oddly...
             configure.arg("no-stdio");
+
+            // Never shared on non-MSVC
+            configure.arg("no-shared");
         }
 
         let os = match target {