Simplify cmake scripts, fix volk_gnsssdr cross-compilation, update ProtocolBuffers to 3.11.2

cmake/Modules/DetectLinuxDistro.cmake

@@ -0,0 +1,99 @@
+# Copyright (C) 2020 (see AUTHORS file for a list of contributors)
+#
+# This file is part of GNSS-SDR.
+#
+# GNSS-SDR is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# GNSS-SDR is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with GNSS-SDR. If not, see <https://www.gnu.org/licenses/>.
+
+if(CMAKE_SIZEOF_VOID_P EQUAL 8)
+    set(ARCH_ "(64 bits)")
+else()
+    set(ARCH_ "(32 bits)")
+endif()
+
+if(EXISTS "/etc/lsb-release")
+    execute_process(COMMAND cat /etc/lsb-release
+        COMMAND grep DISTRIB_ID
+        COMMAND awk -F= "{ print $2 }"
+        COMMAND tr "\n" " "
+        COMMAND sed "s/ //"
+        OUTPUT_VARIABLE LINUX_DISTRIBUTION
+        RESULT_VARIABLE LINUX_ID_RESULT
+    )
+    execute_process(COMMAND cat /etc/lsb-release
+        COMMAND grep DISTRIB_RELEASE
+        COMMAND awk -F= "{ print $2 }"
+        COMMAND tr "\n" " "
+        COMMAND sed "s/ //"
+        OUTPUT_VARIABLE LINUX_VER
+        RESULT_VARIABLE LINUX_VER_RESULT
+    )
+endif()
+
+if(NOT LINUX_DISTRIBUTION)
+    if(EXISTS "/etc/linuxmint/info")
+        set(LINUX_DISTRIBUTION "LinuxMint")
+        execute_process(COMMAND cat /etc/linuxmint/info
+            COMMAND grep -m1 RELEASE
+            COMMAND awk -F= "{ print $2 }"
+            COMMAND tr "\n" " "
+            COMMAND sed "s/ //"
+            OUTPUT_VARIABLE LINUX_VER
+            RESULT_VARIABLE LINUX_VER_RESULT
+        )
+    endif()
+endif()
+
+if(NOT LINUX_DISTRIBUTION)
+    if(EXISTS "/etc/os-release")
+        execute_process(COMMAND cat /etc/os-release
+            COMMAND grep -m1 NAME
+            COMMAND awk -F= "{ print $2 }"
+            COMMAND tr "\n" " "
+            COMMAND sed "s/ //"
+            OUTPUT_VARIABLE LINUX_DISTRIBUTION
+            RESULT_VARIABLE LINUX_ID_RESULT
+        )
+        execute_process(COMMAND cat /etc/os-release
+            COMMAND grep VERSION_ID
+            COMMAND awk -F= "{ print $2 }"
+            COMMAND tr "\n" " "
+            COMMAND sed "s/ //"
+            OUTPUT_VARIABLE LINUX_VER
+            RESULT_VARIABLE LINUX_VER_RESULT
+        )
+        if(${LINUX_DISTRIBUTION} MATCHES "Debian")
+            set(LINUX_DISTRIBUTION "Debian")
+            file(READ /etc/debian_version LINUX_VER)
+        endif()
+    endif()
+endif()
+
+if(NOT LINUX_DISTRIBUTION)
+    if(EXISTS "/etc/redhat-release")
+        set(LINUX_DISTRIBUTION "Red Hat")
+        file(READ /etc/redhat-release LINUX_VER)
+    endif()
+endif()
+
+if(NOT LINUX_DISTRIBUTION)
+    if(EXISTS "/etc/debian_version")
+        set(LINUX_DISTRIBUTION "Debian")
+        file(READ /etc/debian_version LINUX_VER)
+    endif()
+endif()
+
+if(NOT LINUX_DISTRIBUTION)
+    set(LINUX_DISTRIBUTION "Generic")
+    set(LINUX_VER "Unknown")
+endif()