Fix "make -C tests/data_files"
It wasn't working when invoking programs/x509/cert_write or
programs/x509/cert_req due to relying on the current directory rather
than the location of the makefile.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/data_files/Makefile b/tests/data_files/Makefile
index 40c22f5..9d4cca2 100644
--- a/tests/data_files/Makefile
+++ b/tests/data_files/Makefile
@@ -13,8 +13,10 @@
## Tools
OPENSSL ?= openssl
FAKETIME ?= faketime
-MBEDTLS_CERT_WRITE ?= $(PWD)/../../programs/x509/cert_write
-MBEDTLS_CERT_REQ ?= $(PWD)/../../programs/x509/cert_req
+
+TOP_DIR = $(dir $(firstword $(MAKEFILE_LIST)))/../..
+MBEDTLS_CERT_WRITE ?= $(TOP_DIR)/programs/x509/cert_write
+MBEDTLS_CERT_REQ ?= $(TOP_DIR)/programs/x509/cert_req
## Build the generated test data. Note that since the final outputs