libm: Disable float-equal diagnostics

I choose to believe these authors knew what they were doing.

lib/libm/erf_lgamma.c

@@ -24,6 +24,7 @@
  */
 
 #include "fdlibm.h"
+#pragma GCC diagnostic ignored "-Wfloat-equal"
 
 #define __ieee754_logf logf
 

lib/libm/log1pf.c

@@ -18,6 +18,8 @@
 
 #include "libm.h"
 
+#pragma GCC diagnostic ignored "-Wfloat-equal"
+
 static const float
 ln2_hi = 6.9313812256e-01, /* 0x3f317180 */
 ln2_lo = 9.0580006145e-06, /* 0x3717f7d1 */