Add patched recipe for SOCI: (#4510)

SOCI is the C++ database access library. The SOCI recipe was updated in
Conan Center Index (CCI), and it breaks for our choice of options. This
breakage occurs when you build with a fresh Conan cache (e.g. when you
submit a PR, or delete `~/.conan/data`).

* Add a custom Conan recipe for SOCI v4.0.3
* Update dependency building to handle exporting and installing Snappy
  and SOCI
  * Fix workflows to use custom SOCI recipe
* Update BUILD.md to include instruction for exporting the SOCI Conan
  recipe:
  * `conan export external/soci soci/4.0.3@`

This solution has been verified on Ubuntu 20.04 and macOS.

Context:

* There is a compiler error that the `sqlite3.h` header is not available
  when building soci.
* When package B depends on package A, it finds the pieces it needs by
  importing the Package Configuration File (PCF) that Conan generates
  for package A.
  * Read the CMake written by package B to check that it is importing
    the PCF correctly and linking its exports correctly.
  * Since this can be difficult, it is often more efficient to check
    https://github.com/conan-io/conan-center-index/issues for package B
    to see if anyone else has seen a similar problem.
  * One of the issues points to a problem area in soci's CMake. To
    confirm the diagnosis, review soci's CMake (after any patches are
    applied) in the Conan build directory `build/$buildId/src/`.
  * Review the Conan-generated PCF in
    `build/$buildId/build/$buildType/generators/`.
  * In this case, the problem was likely (re)introduced by
    https://github.com/conan-io/conan-center-index/pull/17026
* If there is a problem in the source or in the Conan recipe, the
  fastest fix is to copy the recipe and either:
  * Add a source patch to fix any problems in the source.
  * Change the recipe to fix any problems in the recipe.
* In this case, this can be done by finding soci's Conan recipe at
  https://github.com/conan-io/conan-center-index/tree/master/recipes/soci
  and then copying the `all` directory as `external/$packageName` in our
  project. Then, make any changes.
  * Test packages can be removed from the recipe folder as they are not
    needed.
  * If adding a patch in the `patches` directory, add a description for
    it to `conandata.yml`.
  * Since `conanfile.py` has no `version` property on the recipe class,
    builders need to pass a version on the command line (like they do
    for our `snappy` recipe).
* Add an example command to `BUILD.md`.

Future work: It may make sense to refer to recipes by revision, by
checking in a lockfile.

external/soci/patches/0001-Remove-hardcoded-INSTALL_NAME_DIR-for-relocatable-li.patch

@@ -0,0 +1,39 @@
+From d491bf7b5040d314ffd0c6310ba01f78ff44c85e Mon Sep 17 00:00:00 2001
+From: Rasmus Thomsen <rasmus.thomsen@dampsoft.de>
+Date: Fri, 14 Apr 2023 09:16:29 +0200
+Subject: [PATCH] Remove hardcoded INSTALL_NAME_DIR for relocatable libraries
+ on MacOS
+
+---
+ cmake/SociBackend.cmake | 2 +-
+ src/core/CMakeLists.txt | 1 -
+ 2 files changed, 1 insertion(+), 2 deletions(-)
+
+diff --git a/cmake/SociBackend.cmake b/cmake/SociBackend.cmake
+index 5d4ef0df..39fe1f77 100644
+--- a/cmake/SociBackend.cmake
++++ b/cmake/SociBackend.cmake
+@@ -171,7 +171,7 @@ macro(soci_backend NAME)
+           set_target_properties(${THIS_BACKEND_TARGET}
+             PROPERTIES
+             SOVERSION ${${PROJECT_NAME}_SOVERSION}
+-            INSTALL_NAME_DIR ${CMAKE_INSTALL_PREFIX}/lib)
++          )
+ 
+           if(APPLE)
+             set_target_properties(${THIS_BACKEND_TARGET}
+diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
+index 3e7deeae..f9eae564 100644
+--- a/src/core/CMakeLists.txt
++++ b/src/core/CMakeLists.txt
+@@ -59,7 +59,6 @@ if (SOCI_SHARED)
+       PROPERTIES
+       VERSION ${SOCI_VERSION}
+       SOVERSION ${SOCI_SOVERSION}
+-      INSTALL_NAME_DIR ${CMAKE_INSTALL_PREFIX}/lib
+       CLEAN_DIRECT_OUTPUT 1)
+   endif()
+ 
+-- 
+2.25.1
+

external/soci/patches/0002-Fix-soci_backend.patch

@@ -0,0 +1,24 @@
+diff --git a/cmake/SociBackend.cmake b/cmake/SociBackend.cmake
+index 0a664667..3fa2ed95 100644
+--- a/cmake/SociBackend.cmake
++++ b/cmake/SociBackend.cmake
+@@ -31,14 +31,13 @@ macro(soci_backend_deps_found NAME DEPS SUCCESS)
+     if(NOT DEPEND_FOUND)
+       list(APPEND DEPS_NOT_FOUND ${dep})
+     else()
+-      string(TOUPPER "${dep}" DEPU)
+-      if( ${DEPU}_INCLUDE_DIR )
+-        list(APPEND DEPS_INCLUDE_DIRS ${${DEPU}_INCLUDE_DIR})
++      if( ${dep}_INCLUDE_DIR )
++        list(APPEND DEPS_INCLUDE_DIRS ${${dep}_INCLUDE_DIR})
+       endif()
+-      if( ${DEPU}_INCLUDE_DIRS )
+-        list(APPEND DEPS_INCLUDE_DIRS ${${DEPU}_INCLUDE_DIRS})
++      if( ${dep}_INCLUDE_DIRS )
++        list(APPEND DEPS_INCLUDE_DIRS ${${dep}_INCLUDE_DIRS})
+       endif()
+-      list(APPEND DEPS_LIBRARIES ${${DEPU}_LIBRARIES})
++      list(APPEND DEPS_LIBRARIES ${${dep}_LIBRARIES})
+     endif()
+   endforeach()
+