Add poseidon2 dependency (#625)

* [build] add nim-poseidon2

* [build] Workaround incompatibility constantine and secp256k1

Constantine sets compiler flag that is incompatible
with the assembly code in secp256k1:
https://github.com/mratsim/constantine/blob/5f7ba18f2ed351260015397c9eae079a6decaee1/constantine/platforms/isa/macro_assembler_x86.nim#L19

---------

Co-authored-by: Dmitriy Ryajov <dryajov@gmail.com>

.gitmodules

@@ -193,3 +193,9 @@
 [submodule "vendor/npeg"]
 	path = vendor/npeg
 	url = https://github.com/zevv/npeg
+[submodule "vendor/nim-poseidon2"]
+	path = vendor/nim-poseidon2
+	url = https://github.com/codex-storage/nim-poseidon2.git
+[submodule "vendor/constantine"]
+	path = vendor/constantine
+	url = https://github.com/mratsim/constantine.git

codex.nimble

@@ -30,5 +30,6 @@ requires "leopard >= 0.1.0 & < 0.2.0"
 requires "blscurve"
 requires "libp2pdht"
 requires "eth"
+requires "https://github.com/codex-storage/nim-poseidon2.git >= 0.1.0 & < 0.2.0"
 
 include "build.nims"

config.nims

@@ -113,6 +113,9 @@ switch("define", "libp2p_pki_schemes=secp256k1")
 # we can't use it. And codex.cfg doesn't work
 switch("define", "chronicles_sinks=textlines[dynamic],json[dynamic],textlines[dynamic]")
 
+# Workaround for assembler incompatibility between constantine and secp256k1
+switch("define", "use_asm_syntax_intel=false")
+
 # begin Nimble config (version 1)
 when system.fileExists("nimble.paths"):
   include "nimble.paths"