Doc: Workarounds for Linux build errors (#4409)

BUILD.md

@@ -24,7 +24,7 @@ There are also a few forks of existing packages under the "fork-*" name.
 - macOS, Linux: Install rsync - https://nodejs.org/en/
 - macOS: Install Cocoapods - `brew install cocoapods`
 - Windows: Install Windows Build Tools - `npm install -g windows-build-tools`
-- Linux: Install dependencies - `sudo apt install libnss3 libsecret-1-dev`
+- Linux: Install dependencies - `sudo apt install libnss3 libsecret-1-dev python`
 
 ## Building
 
@@ -110,4 +110,4 @@ It still requires you to quit the application each time you want it to rebuild,
 
 # Troubleshooting
 
-Please read for the [Build Troubleshooting Document](https://github.com/laurent22/joplin/blob/dev/readme/build_troubleshooting.md) for various tips on how to get the build working.
+Please read for the [Build Troubleshooting Document](https://github.com/laurent22/joplin/blob/dev/readme/build_troubleshooting.md) for various tips on how to get the build working.

readme/build_troubleshooting.md

@@ -19,6 +19,16 @@ If there's an error `while loading shared libraries: libgconf-2.so.4: cannot ope
 
 If you get a node-gyp related error, you might need to manually install it: `npm install -g node-gyp`.
 
+If you get unexpected `npm` dependency errors on a fresh git pull, try `npm run clean`
+
+If `npm i` gives you a fatal error like the following:
+```
+node-pre-gyp WARN Tried to download(403): https://mapbox-node-binary.s3.amazonaws.com/sqlite3/v5.0.1/napi-v6-linux-x64.tar.gz 
+node-pre-gyp WARN Pre-built binaries not found for sqlite3@5.0.1 and node@14.15.4 (node-v83 ABI, glibc) (falling back to source compile with node-gyp)
+/bin/sh: 1: python: not found
+```
+Try `sudo apt install python` (or the `apt` equivalent for your operating system) and then run `npm i` again.
+
 If you get the error `libtool: unrecognized option '-static'`, follow the instructions [in this post](https://stackoverflow.com/a/38552393/561309) to use the correct libtool version.
 
 ## Other issues