Output clang root dir instead of 'auto'. Remove trailing spaces and add BSC header

Author: mikaoP

m4/clang.m4

@@ -1,3 +1,7 @@
+#	This file is part of Nanos6 and is licensed under the terms contained in the COPYING file.
+#
+#	Copyright (C) 2020 Barcelona Supercomputing Center (BSC)
+
 AC_DEFUN([SSS_CHECK_NANOS6_CLANG],
 	[
 		AC_ARG_WITH(
@@ -6,7 +10,7 @@ AC_DEFUN([SSS_CHECK_NANOS6_CLANG],
 			[ac_use_nanos6_clang_prefix="${withval}"],
 			[ac_use_nanos6_clang_prefix="auto"]
 		)
-		
+
 		if test x"${ac_use_nanos6_clang_prefix}" = x"auto" || test x"${ac_use_nanos6_clang_prefix}" = x"yes" ; then
 			AC_PATH_PROGS(NANOS6_CLANG, [clang], [])
 			AC_PATH_PROGS(NANOS6_CLANGXX, [clang++], [])
@@ -18,6 +22,7 @@ AC_DEFUN([SSS_CHECK_NANOS6_CLANG],
 					ac_have_nanos6_clang=no
 				fi
 			else
+				ac_use_nanos6_clang_prefix=$(echo "${NANOS6_CLANG}" | sed 's@/bin/clang@@')
 				ac_have_nanos6_clang=yes
 			fi
 		elif test x"${ac_use_nanos6_clang_prefix}" != x"no" ; then
@@ -26,27 +31,28 @@ AC_DEFUN([SSS_CHECK_NANOS6_CLANG],
 			if test x"${NANOS6_CLANG}" = x"" || test x"${NANOS6_CLANGXX}" = x"" ; then
 				AC_MSG_ERROR([could not find Nanos6 Clang])
 			else
+				ac_use_nanos6_clang_prefix=$(echo "${NANOS6_CLANG}" | sed 's@/bin/clang@@')
 				ac_have_nanos6_clang=yes
 			fi
 		else
 			ac_use_nanos6_clang_prefix=""
 			ac_have_nanos6_clang=no
 		fi
-		
+
 		AC_MSG_CHECKING([the Nanos6 Clang installation prefix])
 		if test x"${ac_have_nanos6_clang}" = x"yes" ; then
 			AC_MSG_RESULT([${ac_use_nanos6_clang_prefix}])
 		else
 			AC_MSG_RESULT([not found])
 		fi
-		
+
 		if test x"${NANOS6_CLANG}" != x"" ; then
 			ac_save_CC="${CC}"
 			AC_LANG_PUSH(C)
-			
+
 			AC_MSG_CHECKING([which flag enables OmpSs-2 support in Clang])
 			OMPSS2_FLAG=none
-			
+
 			CC="${NANOS6_CLANG} -fompss-2"
 			AC_COMPILE_IFELSE(
 				[ AC_LANG_SOURCE( [[
@@ -58,7 +64,7 @@ int main(int argc, char ** argv) {
 				[ OMPSS2_FLAG=-fompss-2 ],
 				[ ]
 			)
-			
+
 			if test x"${OMPSS2_FLAG}" != x"none" ; then
 				AC_MSG_RESULT([${OMPSS2_FLAG}])
 				NANOS6_CLANG="${NANOS6_CLANG} ${OMPSS2_FLAG} --gcc-toolchain=\$(subst bin/gcc,,\$(shell which gcc))"
@@ -72,17 +78,17 @@ int main(int argc, char ** argv) {
 				unset ac_use_nanos6_clang_prefix
 				ac_have_nanos6_clang=no
 			fi
-			
+
 			AC_LANG_POP(C)
 			CC="${ac_save_CC}"
-			
+
 		fi
-		
+
 		NANOS6_CLANG_PREFIX="${ac_use_nanos6_clang_prefix}"
 		AC_SUBST([NANOS6_CLANG_PREFIX])
 		AC_SUBST([NANOS6_CLANG])
 		AC_SUBST([NANOS6_CLANGXX])
-		
+
 		AM_CONDITIONAL(HAVE_NANOS6_CLANG, test x"${ac_have_nanos6_clang}" = x"yes")
 	]
 )