build: Add "make lsp" command

Generates the compile_commands.json file using the "bear" application so the
ccls server can be more efficient with our code base.

Closes #40227

Signed-off-by: David Goulet <dgoulet@torproject.org>

scripts/maint/gen_ccls_file.sh

@@ -0,0 +1,20 @@
+#!/bin/sh
+
+##############################################################################
+# THIS MUST BE CALLED FROM THE ROOT DIRECTORY. IT IS USED BY THE MAKEFILE SO #
+# IN THEORY, YOU SHOULD NEVER CALL THIS.                                     #
+##############################################################################
+
+set -e
+
+CCLS_FILE=".ccls"
+
+# Get all #define *_PRIVATE from our source. We need to list them in our .ccls
+# file and enable them otherwise ccls will not find their definition thinking
+# that they are dead code.
+PRIVATE_DEFS=$(grep -r --include \*.h "_PRIVATE" | grep "#ifdef" | cut -d' ' -f2 | sort | uniq)
+
+echo "clang" > "$CCLS_FILE"
+for p in $PRIVATE_DEFS; do
+  echo "-D$p" >> "$CCLS_FILE"
+done