add nvhpc compiler support (flame#719)

Add detection of the NVIDIA nvhpc compiler (`nvc`) in `configure`, and adjust some warning options in `config.mk`. Currently, no specific options for `nvc` have been added in the relevant configurations so it may not be usable without further tweaks.

common.mk

@@ -719,7 +719,11 @@ CWARNFLAGS :=
 # Disable unused function warnings and stop compiling on first error for
 # all compilers that accept such options: gcc, clang, and icc.
 ifneq ($(CC_VENDOR),ibm)
+ifneq ($(CC_VENDOR),nvc)
 CWARNFLAGS += -Wall -Wno-unused-function -Wfatal-errors
+else
+CWARNFLAGS += -Wall -Wno-unused-function
+endif
 endif
 
 # Disable tautological comparision warnings in clang.

config/generic/make_defs.mk

@@ -71,7 +71,11 @@ else
 ifeq ($(CC_VENDOR),clang)
 CKVECFLAGS     :=
 else
-$(error gcc, icc, or clang is required for this configuration.)
+ifeq ($(CC_VENDOR),nvc)
+CKVECFLAGS     :=
+else
+$(error gcc, icc, nvc, or clang is required for this configuration.)
+endif
 endif
 endif
 endif

configure

@@ -1545,7 +1545,7 @@ get_compiler_version()
 	# The last part ({ read first rest ; echo $first ; }) is a workaround
 	# to OS X's egrep only returning the first match.
 	cc_vendor=$(echo "${vendor_string}" |
-	            grep -oE 'icc|gcc|clang|emcc|pnacl|IBM|oneAPI|crosstool-NG|GCC' |
+	            grep -oE 'icc|gcc|clang|nvc|emcc|pnacl|IBM|oneAPI|crosstool-NG|GCC' |
 	            { read -r first rest ; echo "${first}"; })
 
 	# AOCC version strings contain both "clang" and "AOCC" substrings, and