Add bits to openlibm headers to switch between using the host headers.

src/openlibm.h

@@ -14,6 +14,10 @@
  * $FreeBSD: src/lib/msun/src/openlibm.h,v 1.82 2011/11/12 19:55:48 theraven Exp $
  */
 
+#ifdef OPENLIBM_USE_HOST_MATH_H
+#include <math.h>
+#else /* !OPENLIBM_USE_HOST_MATH_H */
+
 #ifndef OPENLIBM_H
 #define	OPENLIBM_H
 
@@ -487,3 +491,5 @@ long double	lgammal_r(long double, int *);
 }
 #endif
 #endif /* !OPENLIBM_H */
+
+#endif /* OPENLIBM_USE_HOST_MATH_H */

src/openlibm_complex.h

@@ -15,6 +15,10 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
+#ifdef OPENLIBM_USE_HOST_COMPLEX_H
+#include <complex.h>
+#else /* !OPENLIBM_USE_HOST_COMPLEX_H */
+
 #ifndef OPENLIBM_COMPLEX_H
 #define	OPENLIBM_COMPLEX_H
 
@@ -171,3 +175,5 @@ long double complex cprojl(long double complex);
 long double creall(long double complex);
 
 #endif /* !OPENLIBM_COMPLEX_H */
+
+#endif /* OPENLIBM_USE_HOST_COMPLEX_H */

src/openlibm_fenv.h

@@ -1,3 +1,7 @@
+#ifdef OPENLIBM_USE_HOST_FENV_H
+#include <fenv.h>
+#else /* !OPENLIBM_USE_HOST_FENV_H */
+
 #if defined(__arm__)
 #include "../arm/fenv.h"
 #elif defined(__x86_64__)
@@ -7,3 +11,5 @@
 #else
 #error "Unsupported platform"
 #endif
+
+#endif /* OPENLIBM_USE_HOST_FENV_H */