update GCC version default minimum to 10.1.0

1. The GCC version can still be overriden for users who want
   to build OpenCoarrays with an older version by passing the
   -f, -c, and -C arguments or their longer equivalents.
2. Updaing the GCC version ensures co_broadcast handles
   derived-type arguments.
3. This commit also updates the gcc download to use git to fix
   the problem of ftp being present and therefore chosen as the
   default even though ftp access is blocked by a user's network
   (for security reasons).

Author: Damian Rouson

install.sh-usage

@@ -1,4 +1,4 @@
-  -b --install-branch [arg]   Install the specified repository development branch (Examples: -b trunk or -b gcc-7-branch).
+  -b --install-branch [arg]   Install the specified repository development branch (Examples: -b master).
   -c --with-c [arg]           Use specified C compiler (Example: -c /usr/local/bin/gcc).
   -C --with-cxx [arg]         Use specified C++ compiler (Example: -C /usr/local/bin/g++).
   -d --debug                  Enable debug mode.

prerequisites/build-functions/set_or_print_default_version.sh

@@ -27,7 +27,7 @@ set_or_print_default_version()
   # See http://stackoverflow.com/questions/1494178/how-to-define-hash-tables-in-bash
   package_version=(
     "cmake:3.10.0"
-    "gcc:8.3.0"
+    "gcc:10.1.0"
     "mpich:3.2"
     "wget:1.16.3"
     "flex:2.6.0"

prerequisites/build-functions/set_or_print_downloader.sh

@@ -7,17 +7,19 @@ set_or_print_downloader()
 {
   # Verify requirements
   [ ! -z "${arg_D}" ] && [ ! -z "${arg_p:-${arg_P:-${arg_U:-${arg_V}}}}" ] &&
-    emergency "Please pass only one of {-B, -D, -p, -P, -U, -V} or a longer equivalent (multiple detected)."
+    emergency "Please pass only one of {-D, -p, -P, -U, -V} or a longer equivalent (multiple detected)."
 
   package_name="${arg_p:-${arg_D:-${arg_P:-${arg_U:-${arg_V}}}}}"
 
-  if [[ "${package_name}" == "ofp" ]]; then
+  if [[ "${package_name}" == "gcc" ]]; then
+    arg_b=${arg_b:-releases/gcc-${version_to_build}}
+  elif [[ "${package_name}" == "ofp" ]]; then
     "${OPENCOARRAYS_SRC_DIR}/prerequisites/install-ofp.sh" "${@}"
     exit 0
   fi
 
   # Choose the first available download mechanism, prioritizing first any absolute requirement
-  # (git for gcc development branches) and second robustness:
+  # (git for gcc) and second robustness:
   info "Checking available download mechanisms: ftp, wget, and curl."
   info "\${package_name}=${package_name}  \${arg_b:-}=${arg_b:-}"
 
@@ -26,15 +28,15 @@ set_or_print_downloader()
   elif type wget &> /dev/null; then
     gcc_prereqs_fetch=wget
   elif type ftp &> /dev/null; then
-    if [[ "${package_name}" == "gcc"   || "${package_name}" == "wget" || "${package_name}" == "make" ||
+    if [[ "${package_name}" == "wget" || "${package_name}" == "make" ||
           "${package_name}" == "bison" || "${package_name}" == "m4"   ]]; then
       gcc_prereqs_fetch=ftp_url
     fi
   else
     tried="curl, wget, and ftp"
   fi
 
-  if [[ "${package_name}" == "gcc" && ! -z "${arg_b}" ]]; then
+  if [[ "${package_name}" == "gcc" ]]; then
     if type git &> /dev/null; then
       fetch=git
     else
@@ -45,7 +47,7 @@ set_or_print_downloader()
   fi
 
   if [[ -z "${fetch:-}" ]]; then
-    emergency "No available download mechanism. Option tried: ${tried}"
+    emergency "No available download mechanism. Option(s) tried: ${tried}"
   fi
 
   # If a printout of the download mechanism was requested, then print it and exit with normal status

prerequisites/build-functions/set_or_print_url.sh

@@ -19,15 +19,9 @@ else
 
   if [[ "${package_to_build}" == 'cmake' ]]; then
     major_minor="${version_to_build%.*}"
-  elif [[ "${package_to_build}" == "gcc" ]]; then
-    if [[ -z "${arg_b}" ]]; then
-      gcc_url_head="https://ftpmirror.gnu.org/gcc/gcc-${version_to_build}/"
-    else
-      gcc_url_head="git://gcc.gnu.org/git/"
-    fi
   fi
   package_url_head=(
-    "gcc;${gcc_url_head-}"
+    "gcc;https://gcc.gnu.org/git/"
     "wget;https://ftpmirror.gnu.org/gnu/wget/"
     "m4;https://ftpmirror.gnu.org/gnu/m4/"
     "pkg-config;https://pkgconfig.freedesktop.org/releases/"
@@ -51,15 +45,8 @@ else
   done
 
   # Set differing tails for GCC release downloads versus development branch checkouts
-  if [[ "${package_to_build}" == 'gcc' ]]; then
-    if [[ "${fetch}" == 'git' ]]; then
-      gcc_tail="gcc"
-    else
-      gcc_tail="gcc-${version_to_build}.tar.gz"
-    fi
-  fi
   package_url_tail=(
-    "gcc;${gcc_tail-}"
+    "gcc;gcc.git"
     "wget;wget-${version_to_build-}.tar.gz"
     "m4;m4-${version_to_build-}.tar.bz2"
     "pkg-config;pkg-config-${version_to_build-}.tar.gz"

prerequisites/build.sh-usage

@@ -1,5 +1,4 @@
-  -b --install-branch [arg]   Install the specified repository development branch.
-  -B --list-branches [arg]    List the available branches in the specified package's repository.
+  -b --install-branch [arg]   Install the specified repository development branch (Examples: -b master).
   -c --with-c [arg]           Use the specified C compiler. Default="gcc"
   -C --with-cxx [arg]         Use the specified C++ compiler. Default="g++"
   -d --debug                  Enable debug mode.