Add more intermediate files/paths to .gitignore.

Change-Id: I5af202b9536cc120968a57a4daf6d899f6b35b87
diff --git a/.gitignore b/.gitignore
index 09c354a..4981783 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,24 @@
+# Downloaded source archives
 archives
+
+# Expanded source directories
+binutils-[0-9]*
+gcc-[0-9]*
+gdb-[0-9]*
+gmp-[0-9]*
+mpc-[0-9]*
+mpfr-[0-9]*
+
+# Build directories
+build-*
+
+# Installation directories
+aarch64-elf-*-Linux-*
+arm-eabi-*-Linux-*
+i386-elf-*-Linux-*
+x86_64-elf-*-Linux-*
+
+# Miscellaneous artifacts
+build.log
+.extracted-stamp
+