build: install aclocal files

Installing aclocal files enables downstream patches to be applied simpler, as
the macros at build machine's /usr/share/aclocal are copied into package m4/
directory.

For example the ax_code_coverage.m4 broke backward compatibility in recent
version, distributing this within package reduce dependencies and makes it
easier to run autoreconf.

Signed-off-by: Alon Bar-Lev <alon.barlev@gmail.com>

diff --git a/Dockerfile b/Dockerfile
index 19dcae3..0d12f5c 100644
--- a/Dockerfile
+++ b/Dockerfile

@@ -46,11 +46,12 @@
 # TPM2-TSS
 COPY . /tmp/tpm2-tss/
 WORKDIR /tmp/tpm2-tss
-RUN ./bootstrap -I /usr/share/gnulib/m4 \
+ENV LD_LIBRARY_PATH /usr/local/lib
+ENV ACLOCAL_PATH /usr/share/gnulib/m4
+RUN ./bootstrap \
 	&& ./configure --enable-unit \
 	&& make -j$(nproc) check \
 	&& make install \
 	&& ldconfig
-ENV LD_LIBRARY_PATH /usr/local/lib
 RUN cat test-suite.log