Add complex return detection for nvfortran (flame#765)

Details:
- Search for Intel ifx and NVIDIA/PGI Fortran compilers.
- Correctly determine the Fortran compiler vendor for Intel ifx and NVIDIA/PGI compilers.
- Determine the compiler version and correct Fortran complex return type for NVIDIA/PGI.

configure

@@ -1221,7 +1221,7 @@ get_fc_search_list()
 {
 	local list
 
-	list="gfortran ifort"
+	list="gfortran ifort ifx nvfortran"
 
 	echo "${list}"
 }
@@ -4229,11 +4229,37 @@ blis_main()
 			# Query the compiler "vendor" (ie: the compiler's simple name).
 			# The last part ({ read first rest ; echo $first ; }) is a workaround
 			# to OS X's egrep only returning the first match.
-			fc_vendor=$(echo "${vendor_string}" | grep -oE 'IFORT|GNU' |
+			fc_vendor=$(echo "${vendor_string}" | grep -oE 'IFORT|IFX|GNU|NVIDIA|PGI' |
 			            { read -r first rest ; echo "${first}"; })
 
-			if [[ ${fc_vendor} = IFORT ]]; then
+			if [[ ${fc_vendor} = IFORT || ${fc_vendor} = IFX ]]; then
 				complex_return='intel'
+			elif [[ ${fc_vendor} = NVIDIA || ${fc_vendor} = PGI ]]; then
+				# On x86_64 and aarch64 prior to 23.9, nvfortran
+				# uses the 'intel' convention.
+                                # On and ppc64le and aarch64 starting with 23.9,
+                                # the convention is 'gnu'.
+				if [[ "$(uname -m)" = "aarch64" ]]; then
+					fc_version=$(echo "${vendor_string}" \
+					             | grep -oE '[0-9]+\.[0-9]+\.?[0-9]*' \
+					             | { read -r first rest ; echo "${first}"; })
+					if [[ ${fc_version:0:2} -lt 23 ]]; then
+						complex_return='intel'
+					elif [[ ${fc_version:0:2} -eq 23 ]]; then
+						# Use 3:5 because minor version numbers include 1 and 11.
+						if [[ ${fc_version:3:5} -lt 9 ]]; then
+							complex_return='intel'
+						else
+							complex_return='gnu'
+						fi
+					else
+						complex_return='gnu'
+					fi
+				elif [[ "$(uname -m)" = "ppc64le" ]]; then
+					complex_return='gnu'
+				else
+					complex_return='intel'
+				fi
 			elif [[ ${fc_vendor} = GNU ]]; then
 				complex_return='gnu'
 			else