Added FreeBSD build guide from SDKchan.

Building-for-FreeBSD.-.md

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+## One word of caution before proceeding.
+This is not the usual or preferred way to build programs on FreeBSD.  
+As of writing there is no official fresh port available for eden-emu, but it is in the works.  
+After it is available you can find a link to the eden-emu fresh port here and on Escarys github repo.  
+See this build as an App Image alternative for FreeBSD.
+
+## Dependencies.  
+Before we start we need some dependencies.  
+These dependencies are generally needed to build eden-emu on FreeBSD.
+
+```
+devel/cmake  
+devel/sdl20  
+devel/boost-libs  
+devel/catch2  
+devel/libfmt  
+devel/nlohmann-json  
+devel/ninja  
+devel/nasm  
+devel/autoconf  
+devel/pkg-config  
+devel/qt6-base  
+
+multimedia/ffnvcodec-headers  
+multimedia/ffmpeg  
+
+audio/opus  
+
+archivers/liblz4  
+
+lang/gcc12  
+
+graphics/glslang  
+graphics/vulkan-utility-libraries  
+```
+
+---
+
+### Build preparations:  
+Run the following command to clone eden with git:
+```sh
+git clone --recursive https://git.eden-emu.dev/eden-emu/eden
+```
+You usually want to add the `--recursive` parameter as it also takes care of the external dependencies for you.
+
+Now change into the eden directory and create a build directory there:
+```sh
+cd eden
+mkdir build
+```
+
+Change into that build directory:
+```sh
+cd build
+```
+
+Now choose one option either 1 or 2, but not both as one option overwrites the other.
+
+#### 1. Building in Release Mode (usually preferred and the most performant choice):
+```sh
+cmake .. -GNinja -DYUZU_TESTS=OFF
+```
+
+#### 2. Building in Release Mode with debugging symbols (useful if you want to debug errors for a eventual fix):
+```sh
+cmake .. -GNinja -DCMAKE_BUILD_TYPE=RelWithDebInfo -DYUZU_TESTS=ON
+```
+
+Build the emulator locally:
+```sh
+ninja
+```
+
+Optional: If you wish to install eden globally onto your system issue the following command:
+```sh
+sudo ninja install
+```
+OR
+```sh
+doas -- ninja install
+```