Define Linux clang target as toolchain
This change configures the Linux clang -Og target as a toolchain with
args. To support this, all Pigweed variables from pw_vars_default are
made into build args, defined within their respective modules.
The Linux clang target/toolchain is the only one that currently works.
Pigweed's other targets will be ported in later changes.
Change-Id: I051e29fde7577e41a3184c37031a4e04936404e1
diff --git a/.gitignore b/.gitignore
index d799107..4f09cea 100644
--- a/.gitignore
+++ b/.gitignore
@@ -54,4 +54,6 @@
# Web Tools
node_modules
-yarn-error.log
\ No newline at end of file
+yarn-error.log
+
+nanopb