[#35] project: improve dependency handling and re-add git submodules

Due to issues in build environments without a network connection,
it is necessary to allow users to pull phoenix's dependencies before
running any build scripts. By re-adding git submodules for the
dependencies, this can be made possible.

Because working with git submodules on larger projects with many
nested dependencies is a pain, however, phoenix still supports
downloading dependencies while configuring, so using the submodule
approach is not required.

(cherry picked from commit fbb042b)

.gitmodules

@@ -0,0 +1,18 @@
+[submodule "vendor/doctest"]
+	path = vendor/doctest
+	url = https://github.com/doctest/doctest.git
+[submodule "vendor/mio"]
+	path = vendor/mio
+	url = https://github.com/mandreyel/mio.git
+[submodule "vendor/lexy"]
+	path = vendor/lexy
+	url = https://github.com/foonathan/lexy.git
+[submodule "vendor/fmt"]
+	path = vendor/fmt
+	url = https://github.com/fmtlib/fmt.git
+[submodule "vendor/libsquish"]
+	path = vendor/libsquish
+	url = https://github.com/lmichaelis/phoenix-libsquish.git
+[submodule "vendor/glm"]
+	path = vendor/glm
+	url = https://github.com/g-truc/glm.git

vendor/CMakeLists.txt

@@ -1,101 +1,39 @@
 include(FetchContent)
 
-option(BUILD_STATIC_LIBS ON)
-option(BUILD_SHARED_LIBS OFF)
-
-
-# add doctest
-FetchContent_Declare(
-        doctest
-        URL https://github.com/doctest/doctest/archive/refs/tags/v2.4.9.zip
-        URL_HASH SHA1=d1563419fa370c34c90e028c2e903a70c8dc07b2
-)
-
-if (NOT doctest_POPULATED)
-    message(STATUS "Downloading doctest")
-    FetchContent_Populate(doctest)
-    add_subdirectory(${doctest_SOURCE_DIR} ${doctest_BINARY_DIR})
-endif ()
-
-
-# add mio
-FetchContent_Declare(
-        mio
-        URL https://github.com/mandreyel/mio/archive/3f86a95c0784d73ce6815237ec33ed25f233b643.zip
-        URL_HASH SHA1=62a0e43b07a6b66e415ad01f4b225c72a3c9935b
-)
-
-if (NOT mio_POPULATED)
-    message(STATUS "Downloading mio")
-    FetchContent_Populate(mio)
-    add_subdirectory(${mio_SOURCE_DIR} ${mio_BINARY_DIR})
-endif ()
-
-
-# add lexy
-FetchContent_Declare(
-        lexy
-        URL https://github.com/foonathan/lexy/releases/download/v2022.05.1/lexy-src.zip
-        URL_HASH SHA1=252185ebbf004047725f9ed98b4e8b6e4aa06d98
-)
-
-if (NOT lexy_POPULATED)
-    message(STATUS "Downloading lexy")
-    FetchContent_Populate(lexy)
-    add_subdirectory(${lexy_SOURCE_DIR} ${lexy_BINARY_DIR})
-endif ()
-
-
-# add fmt
-FetchContent_Declare(
-        fmt
-        URL https://github.com/fmtlib/fmt/releases/download/9.1.0/fmt-9.1.0.zip
-        URL_HASH SHA1=8de922ba88fccaec1e7778bc069f342084573486
-)
-
-if (NOT fmt_POPULATED)
-    message(STATUS "Downloading fmt")
-    FetchContent_Populate(fmt)
-    add_subdirectory(${fmt_SOURCE_DIR} ${fmt_BINARY_DIR})
-endif ()
-
-
-# add glm
-FetchContent_Declare(
-        glm
-        URL https://github.com/g-truc/glm/releases/download/0.9.9.8/glm-0.9.9.8.zip
-        URL_HASH SHA1=45408897f419944fb28d8fd835791f237be2ec19
-)
-
-if (NOT glm_POPULATED)
-    message(STATUS "Downloading glm")
-    FetchContent_Populate(glm)
-    add_subdirectory(${glm_SOURCE_DIR} ${glm_BINARY_DIR})
-endif ()
+set(BUILD_STATIC_LIBS ON)
+set(BUILD_SHARED_LIBS OFF)
+set(BUILD_SQUISH_WITH_OPENMP OFF CACHE BOOL "" FORCE)
+
+function(px_add_dependency NAME URL URL_HASH)
+    if (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${NAME}/CMakeLists.txt)
+        add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/${NAME})
+        set(${NAME}_SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/${NAME} PARENT_SCOPE)
+    else ()
+        FetchContent_Declare(
+                ${NAME}
+                URL ${URL}
+                URL_HASH SHA1=${URL_HASH}
+        )
+
+        if (NOT ${NAME}_POPULATED)
+            message(STATUS "Downloading ${NAME}")
+            FetchContent_Populate(${NAME})
+            add_subdirectory(${${NAME}_SOURCE_DIR} ${${NAME}_BINARY_DIR})
+        endif ()
+    endif ()
+endfunction()
 
+px_add_dependency(doctest https://github.com/doctest/doctest/archive/refs/tags/v2.4.9.zip d1563419fa370c34c90e028c2e903a70c8dc07b2)
+px_add_dependency(mio https://github.com/mandreyel/mio/archive/3f86a95c0784d73ce6815237ec33ed25f233b643.zip 62a0e43b07a6b66e415ad01f4b225c72a3c9935b)
+px_add_dependency(lexy https://github.com/foonathan/lexy/releases/download/v2022.05.1/lexy-src.zip 252185ebbf004047725f9ed98b4e8b6e4aa06d98)
+px_add_dependency(fmt https://github.com/fmtlib/fmt/releases/download/9.1.0/fmt-9.1.0.zip 8de922ba88fccaec1e7778bc069f342084573486)
+px_add_dependency(glm https://github.com/g-truc/glm/releases/download/0.9.9.8/glm-0.9.9.8.zip 45408897f419944fb28d8fd835791f237be2ec19)
+px_add_dependency(libsquish https://downloads.sourceforge.net/project/libsquish/libsquish-1.15.tgz 51844b9a8bc815a27e2cc0ffbede5fee3ef75110)
 
 # msvc: disable -wno-* flags
 if (NOT MSVC)
     target_compile_options(mio INTERFACE -Wno-conversion)
+    target_compile_options(squish PRIVATE -Wno-unused-but-set-variable)
 endif ()
 
-# add libsquish
-FetchContent_Declare(
-        libsquish
-        URL https://downloads.sourceforge.net/project/libsquish/libsquish-1.15.tgz
-        URL_HASH SHA1=51844b9a8bc815a27e2cc0ffbede5fee3ef75110
-)
-
-if (NOT libsquish_POPULATED)
-    message(STATUS "Downloading squish")
-    FetchContent_Populate(libsquish)
-
-    SET(BUILD_SQUISH_WITH_OPENMP OFF CACHE BOOL "" FORCE)
-    add_subdirectory(${libsquish_SOURCE_DIR} ${libsquish_BINARY_DIR})
-    target_include_directories(squish PUBLIC ${libsquish_SOURCE_DIR})
-
-    # msvc: disable -wno-* flags
-    if (NOT MSVC)
-        target_compile_options(squish PRIVATE -Wno-unused-but-set-variable)
-    endif ()
-endif ()
+target_include_directories(squish PUBLIC ${libsquish_SOURCE_DIR})