Force gcc7 versions as gcc4 doesn't work. Disable libtool.

.travis.yml

@@ -19,15 +19,15 @@ env:
   # triplets come from
   # using BinaryBuilder; triplet.(supported_platforms())
   matrix:
-    - TARGET=i686-linux-gnu
-    - TARGET=x86_64-linux-gnu
-    - TARGET=aarch64-linux-gnu
-    - TARGET=arm-linux-gnueabihf
-    - TARGET=powerpc64le-linux-gnu
-    - TARGET=i686-linux-musl
-    - TARGET=x86_64-linux-musl
-    - TARGET=aarch64-linux-musl
-    - TARGET=arm-linux-musleabihf
+    - TARGET=i686-linux-gnu-gcc7
+    - TARGET=x86_64-linux-gnu-gcc7
+    - TARGET=aarch64-linux-gnu-gcc7
+    - TARGET=arm-linux-gnueabihf-gcc7
+    - TARGET=powerpc64le-linux-gnu-gcc7
+    - TARGET=i686-linux-musl-gcc7
+    - TARGET=x86_64-linux-musl-gcc7
+    - TARGET=aarch64-linux-musl-gcc7
+    - TARGET=arm-linux-musleabihf-gcc7
     - TARGET=x86_64-apple-darwin14
     - TARGET=x86_64-unknown-freebsd11.1
     - TARGET=i686-w64-mingw32-gcc7

build_tarballs.jl

@@ -71,10 +71,12 @@ fi
 ./configure --prefix=$prefix --host=$target \
     --with-geos=$prefix/bin/geos-config \
     --with-proj=$prefix \
+    --without-libtool \
     --with-libz=$prefix \
     --with-sqlite3=$prefix \
     --with-curl=$prefix/bin/curl-config \
     --with-python=no \
+    --with-threads \
     --enable-shared \
     --disable-static \
     "CC=$CC" \