Expose cc-rs no_default_flags for hassle-free cross-compilation (#225)

src/lib.rs

@@ -77,6 +77,7 @@ pub struct Config {
     uses_cxx11: bool,
     always_configure: bool,
     no_build_target: bool,
+    no_default_flags: bool,
     verbose_cmake: bool,
     verbose_make: bool,
     pic: Option<bool>,
@@ -184,6 +185,7 @@ impl Config {
             path: env::current_dir().unwrap().join(path),
             generator: None,
             generator_toolset: None,
+            no_default_flags: false,
             cflags: OsString::new(),
             cxxflags: OsString::new(),
             asmflags: OsString::new(),
@@ -297,6 +299,13 @@ impl Config {
         self
     }
 
+    /// Disables the generation of default compiler flags. The default compiler
+    /// flags may cause conflicts in some cross compiling scenarios.
+    pub fn no_default_flags(&mut self, no_default_flags: bool) -> &mut Config {
+        self.no_default_flags = no_default_flags;
+        self
+    }
+
     /// Sets the host triple for this compilation.
     ///
     /// This is automatically scraped from `$HOST` which is set for Cargo
@@ -515,7 +524,7 @@ impl Config {
             .debug(false)
             .warnings(false)
             .host(&host)
-            .no_default_flags(ndk);
+            .no_default_flags(ndk || self.no_default_flags);
         if !ndk {
             c_cfg.target(&target);
         }
@@ -527,7 +536,7 @@ impl Config {
             .debug(false)
             .warnings(false)
             .host(&host)
-            .no_default_flags(ndk);
+            .no_default_flags(ndk || self.no_default_flags);
         if !ndk {
             cxx_cfg.target(&target);
         }