docs: cgo secp256k1 ldflags

crypto/keys/secp256k1/internal/secp256k1/README.md

@@ -3,3 +3,16 @@
  This package is copied from https://github.com/ethereum/go-ethereum/tree/8fddf27a989e246659fd018ea9be37b2b4f55326/crypto/secp256k1
 
  Unlike the rest of go-ethereum it is [3-clause BSD](https://opensource.org/licenses/BSD-3-Clause) licensed so compatible with our Apache2.0 license. We opt to copy in here rather than depend on go-ethereum to avoid issues with vendoring of the GPL parts of that repository by downstream.
+
+## Duplicate Symbols
+
+If a project makes use of go-ethereum and Cosmos's cgo secp256k1, C linker will fail with duplicated symbols. To avoid
+this `ldflags` must set to allow multiple definitions. This only works with Linux machines.
+
+#### Gcc
+
+ + `go build -tags libsecp256k1_sdk  -ldflags=all="-extldflags=-Wl,--allow-multiple-definition"`
+
+#### Clang
+
+ + `go build -tags libsecp256k1_sdk -ldflags=all="-extldflags=-zmuldefs"`