Added SOPs for upgrading g++ and libs

install-newer-g++.sop

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+How to install multiple versions of c++ (gcc, g++) and set up their aliass on ubuntu
+Refer to https://tuxamito.com/wiki/index.php/Installing_newer_GCC_versions_in_Ubuntu
+
+[ ] Add the repository
+  [ ] sudo add-apt-repository ppa:ubuntu-toolchain-r/test
+  [ ] sudo apt-get update
+
+[ ] Install compilers
+  [ ] sudo apt-get install gcc g++ gcc-7 g++-7 gcc-8 g++-8 gcc-9 g++-9
+
+[ ] Clear any alternatives already in place
+  [ ] sudo update-alternatives --remove-all gcc
+
+[ ] Set up alternatives
+  [ ] sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-7 90 --slave /usr/bin/g++ g++ /usr/bin/g++-7
+  [ ] sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-8 80 --slave /usr/bin/g++ g++ /usr/bin/g++-8
+  [ ] sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-9 70 --slave /usr/bin/g++ g++ /usr/bin/g++-9
+
+[ ] Configure the compiler to use
+  [ ] sudo update-alternatives --config gcc
+      This will show choices along with the current selected compiler version
+    [ ] Pick the compiler version you want to use
+    [ ] Verify the choice
+      [ ] g++ -v
+

upgrade-c++-libs.sop

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+How to fix libstdc++.so.6: version `GLIBCXX_3.4.26' not found
+
+[ ] Install latest c++ libraries
+  [ ] sudo add-apt-repository ppa:ubuntu-toolchain-r/test
+  [ ] sudo apt-get update
+  [ ] sudo apt upgrade libstdc++6