Adjust to work on systems without CMPLX

---
Signed-off-by: Michael Ferguson <mppf@users.noreply.github.com>

frontend/lib/immediates/complex-support.c

@@ -21,16 +21,56 @@
 
 #include <complex.h>
 
+static double complex makeDoubleComplex(double re, double im) {
+  // Some test environments don't have a working CMPLXF
+  // so use another way to set if needed.
+#if defined(CMPLX)
+  return CMPLX(re, im);
+#else
+#ifndef CHPL_DONT_USE_CMPLX_PTR_ALIASING
+#define cmplx_re64(c) (((double *)&(c))[0])
+#define cmplx_im64(c) (((double *)&(c))[1])
+  double complex val;
+  cmplx_re64(val) = re;
+  cmplx_im64(val) = im;
+  return val;
+#else
+  // This can generate bad values in the face of inf/nan values
+  return re + im*_Complex_I;
+#endif
+#endif
+}
+
+static float complex makeFloatComplex(float re, float im) {
+  // Some test environments don't have a working CMPLXF
+  // so use another way to set if needed.
+#if defined(CMPLXF)
+  return CMPLXF(re, im);
+#else
+#ifndef CHPL_DONT_USE_CMPLX_PTR_ALIASING
+#define cmplx_re32(c) (((float *)&(c))[0])
+#define cmplx_im32(c) (((float *)&(c))[1])
+  float complex val;
+  cmplx_re32(val) = re;
+  cmplx_im32(val) = im;
+  return val;
+#else
+  // This can generate bad values in the face of inf/nan values
+  return re + im*_Complex_I;
+#endif
+#endif
+}
+
 struct complex64 complexSqrt64(struct complex64 x) {
-  float complex c = CMPLXF(x.r, x.i);
+  float complex c = makeFloatComplex(x.r, x.i);
   float complex n = csqrtf(c);
   struct complex64 ret;
   ret.r = crealf(n);
   ret.i = cimagf(n);
   return ret;
 }
 struct complex128 complexSqrt128(struct complex128 x) {
-  double complex c = CMPLX(x.r, x.i);
+  double complex c = makeDoubleComplex(x.r, x.i);
   double complex n = csqrt(c);
   struct complex128 ret;
   ret.r = creal(n);