gitignore: Add Secure/Trusted Boot build files

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>

.gitignore

@@ -12,6 +12,7 @@ skiboot.lds
 skiboot.lid
 skiboot.lid.xz
 skiboot*.map
+skiboot*.stb
 skiboot.info
 coverage-report/
 extract-gcov
@@ -73,6 +74,7 @@ libflash/test/test-blocklevel
 libflash/test/test-flash
 libflash/test/test-ecc
 libflash/test/test-flash-gcov
+libstb/create-container
 libstb/test/run-stb-container
 libstb/test/*-gcov
 test/hello_world/hello_kernel/hello_kernel