Squashed 'src/secp256k1/' changes from 642c885b61..2f2ccc4695

2f2ccc4695 Merge bitcoin-core/secp256k1#1600: cmake: Introduce `SECP256K1_APPEND_LDFLAGS` variable
421ed1b46f cmake: Introduce `SECP256K1_APPEND_LDFLAGS` variable
1988855079 Merge bitcoin-core/secp256k1#1586: fix: remove duplicate 'the' from header file comment
b307614401 Merge bitcoin-core/secp256k1#1583: ci: Bump GCC_SNAPSHOT_MAJOR to 15
fa67b6752d refactor: Use array initialization for unterminated strings
9b0f37bff1 fix: remove duplicate 'the' from header file comment
e34b476730 ci: Bump GCC_SNAPSHOT_MAJOR to 15
3fdf146bad Merge bitcoin-core/secp256k1#1578: ci: Silent Homebrew's noisy reinstall warnings
f8c1b0e0e6 Merge bitcoin-core/secp256k1#1577: release cleanup: bump version after 0.5.1
7057d3c9af ci: Silent Homebrew's noisy reinstall warnings
c3e40d75db release cleanup: bump version after 0.5.1

git-subtree-dir: src/secp256k1
git-subtree-split: 2f2ccc469540fde6495959cec061e95aab033148

CMakeLists.txt

@@ -560,6 +560,14 @@ if(SECP256K1_APPEND_LDFLAGS)
   string(APPEND CMAKE_C_LINK_EXECUTABLE " ${SECP256K1_APPEND_LDFLAGS}")
 endif()
 
+set(SECP256K1_APPEND_LDFLAGS "" CACHE STRING "Linker flags that are appended to the command line after all other flags added by the build system. This variable is intended for debugging and special builds.")
+if(SECP256K1_APPEND_LDFLAGS)
+  # Appending to this low-level rule variable is the only way to
+  # guarantee that the flags appear at the end of the command line.
+  string(APPEND CMAKE_C_CREATE_SHARED_LIBRARY " ${SECP256K1_APPEND_LDFLAGS}")
+  string(APPEND CMAKE_C_LINK_EXECUTABLE " ${SECP256K1_APPEND_LDFLAGS}")
+endif()
+
 add_subdirectory(src)
 if(SECP256K1_BUILD_EXAMPLES)
   add_subdirectory(examples)