Allow selecting the target to build

This is useful to investiage coredumps.

python/README.rst

@@ -114,6 +114,14 @@ The ``run-integration-tests.sh`` script will automatically use
 .. _`deltachat-core-rust github repository`: https://github.com/deltachat/deltachat-core-rust
 .. _`deltachat-core`: https://github.com/deltachat/deltachat-core-rust
 
+Running test using a debug build
+--------------------------------
+
+If you need to examine e.g. a coredump you may want to run the tests
+using a debug build::
+
+   DCC_RS_TARGET=debug ./run-integration-tests.sh -e py37 -- -x -v -k failing_test
+
 
 Building manylinux1 wheels
 ==========================

python/src/deltachat/_build.py

@@ -8,9 +8,10 @@ import cffi
 
 def ffibuilder():
     projdir = os.environ.get('DCC_RS_DEV')
+    target = os.environ.get('DCC_RS_TARGET', 'release')
     if projdir:
         libs = []
-        objs = [os.path.join(projdir, 'target', 'release', 'libdeltachat.a')]
+        objs = [os.path.join(projdir, 'target', target, 'libdeltachat.a')]
         incs = [os.path.join(projdir, 'deltachat-ffi')]
     else:
         libs = ['deltachat']

run-integration-tests.sh

@@ -10,13 +10,10 @@
 #
 #   ./run-integration-tests.sh -e py35 -- -x
 
-cargo build -p deltachat_ffi --release
+cargo build -p deltachat_ffi
 
-# CFLAGS=-I`pwd`/deltachat-ffi
-# LD_LIBRARY_PATH=`pwd`/target/release
-# export CFLAGS
-# export LD_LIBRARY_PATH
 export DCC_RS_DEV=$(pwd)
+export DCC_RS_TARGET=${DCC_RS_TARGET:-release}
 
 pushd python
 toxargs="$@"