fixup! [libc][math] Optimize nearest integer functions using builtins when available

Fix check_builtin_ceil_floor_trunc.cpp not checking for __builtin_floor{,f}.

Author: overmighty

libc/cmake/modules/compiler_features/check_builtin_ceil_floor_trunc.cpp

@@ -1,9 +1,9 @@
 float try_builtin_ceilf(float x) { return __builtin_ceilf(x); }
-float try_builtin_floorf(float x) { return __builtin_ceilf(x); }
+float try_builtin_floorf(float x) { return __builtin_floorf(x); }
 float try_builtin_truncf(float x) { return __builtin_truncf(x); }
 
 double try_builtin_ceil(double x) { return __builtin_ceil(x); }
-double try_builtin_floor(double x) { return __builtin_ceil(x); }
+double try_builtin_floor(double x) { return __builtin_floor(x); }
 double try_builtin_trunc(double x) { return __builtin_trunc(x); }
 
 int main() {}