more robust conan build

CMakeLists.txt

@@ -109,7 +109,9 @@ message (STATUS "Installing dependencies from Conan (this may take some time)...
 conan_cmake_run (CONANFILE conanfile.txt
                  BASIC_SETUP CMAKE_TARGETS
                  BUILD missing
-                 BUILD_TYPE "Release")
+                 BUILD bison
+                 BUILD_TYPE "Release"
+                 SETTINGS compiler.libcxx=libstdc++11)
 #
 # add cnpy temporarily. As long as SaveBoostHistogram does not save to parquet directly
 #

conanfile.txt

 [requires]
-readline/8.0 # this is only needed to fix a missing dependency in "bison" which is pulled-in by arrow
 spdlog/1.8.5
 catch2/2.13.3
 eigen/3.3.8
@@ -9,6 +8,10 @@ proposal/7.0.4
 yaml-cpp/0.6.3
 arrow/2.0.0
 
+[build_requires]
+readline/8.0 # this is only needed to fix a missing dependency in "bison" which is pulled-in by arrow
+bison/[>1.0] # needed for arrow, and we HAVE to compile it
+
 [generators]
 cmake