travis: pass -fPIC when configuring mbedtls

Author: tiennou

script/install-deps-linux.sh

@@ -5,7 +5,8 @@ set -x
 if [ "$MBEDTLS" ]; then
   git clone --depth 10 --single-branch --branch mbedtls-2.6.1 https://github.com/ARMmbed/mbedtls.git ./deps/mbedtls
   cd ./deps/mbedtls
-  cmake -DENABLE_PROGRAMS=OFF -DENABLE_TESTING=OFF -DUSE_SHARED_MBEDTLS_LIBRARY=ON -DUSE_STATIC_MBEDTLS_LIBRARY=OFF .
+  # We pass -fPIC explicitely because we'll include it in libgit2.so
+  CFLAGS=-fPIC cmake -DENABLE_PROGRAMS=OFF -DENABLE_TESTING=OFF -DUSE_SHARED_MBEDTLS_LIBRARY=OFF -DUSE_STATIC_MBEDTLS_LIBRARY=ON .
   cmake --build .
 
   echo "mbedTLS built in `pwd`"