Fix compilation of C++ code for armv7-unknown-linux-gnueabihf (#1298)

Author: tronical

src/lib.rs

@@ -2193,6 +2193,7 @@ impl Build {
                     if target.abi == "eabihf" {
                         // lowest common denominator FPU
                         cmd.args.push("-mfpu=vfpv3-d16".into());
+                        cmd.args.push("-mfloat-abi=hard".into());
                     }
                 }