[PATCH v6 1/3] Makefile: add $(RUST_LIB) prerequisite to osxkeychain

["Shardul Natu via GitGitGadget" <gitgitgadget@gmail.com>]

From: Shardul Natu <snatu@google.com>

When Rust is enabled, the git-credential-osxkeychain helper depends on
Rust symbols compiled into $(RUST_LIB). While commit 522ea8ef7d
("osxkeychain: fix build with Rust") updated the linker command line to
use $(LIBS), it omitted $(RUST_LIB) from the target prerequisite list.
Without this prerequisite, running a parallel build ("make -j") from a
clean working tree can fail because Make does not know to invoke Cargo
to build libgitcore.a before linking git-credential-osxkeychain.

Note that we depend explicitly on $(LIB_FILE) and $(RUST_LIB) rather
than $(GITLIBS). Unlike standard Git builtins and programs like scalar
(which define cmd_main() and rely on common-main.o to supply main()),
git-credential-osxkeychain.c defines its own standalone int main().
If $(GITLIBS) were used, $(filter %.o,$^) in the link recipe would
match both git-credential-osxkeychain.o and common-main.o, causing a
duplicate symbol linking error for _main on macOS.

Additionally, wrap the definitions of $(RUST_LIB) and the "rust" build
target in "ifndef NO_RUST". This ensures that when NO_RUST=1 is
specified, $(RUST_LIB) evaluates to empty, making the Rust dependency a
clean no-op without needing intermediate variables.

Signed-off-by: Shardul Natu <snatu@google.com>
---
 Makefile | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 1f3f099f5c..7db38ecce9 100644
--- a/Makefile
+++ b/Makefile
@@ -939,6 +939,7 @@ TEST_SHELL_PATH = $(SHELL_PATH)
 
 LIB_FILE = libgit.a
 
+ifndef NO_RUST
 ifdef DEBUG
 RUST_TARGET_DIR = target/debug
 else
@@ -950,6 +951,7 @@ RUST_LIB = $(RUST_TARGET_DIR)/gitcore.lib
 else
 RUST_LIB = $(RUST_TARGET_DIR)/libgitcore.a
 endif
+endif
 
 GITLIBS = common-main.o $(LIB_FILE)
 EXTLIBS =
@@ -3019,11 +3021,13 @@ scalar$X: scalar.o GIT-LDFLAGS $(GITLIBS)
 $(LIB_FILE): $(LIB_OBJS)
 	$(QUIET_AR)$(RM) $@ && $(AR) $(ARFLAGS) $@ $^
 
+ifndef NO_RUST
 $(RUST_LIB): Cargo.toml $(RUST_SOURCES) $(LIB_FILE)
 	$(QUIET_CARGO)cargo build $(CARGO_ARGS)
 
 .PHONY: rust
 rust: $(RUST_LIB)
+endif
 
 export DEFAULT_EDITOR DEFAULT_PAGER
 
@@ -4074,7 +4078,8 @@ $(LIBGIT_HIDDEN_EXPORT): $(LIBGIT_PARTIAL_EXPORT)
 contrib/libgit-sys/libgitpub.a: $(LIBGIT_HIDDEN_EXPORT)
 	$(AR) $(ARFLAGS) $@ $^
 
-contrib/credential/osxkeychain/git-credential-osxkeychain: contrib/credential/osxkeychain/git-credential-osxkeychain.o $(LIB_FILE) GIT-LDFLAGS
+# When Rust is enabled, git-credential-osxkeychain depends on Rust symbols in $(RUST_LIB)
+contrib/credential/osxkeychain/git-credential-osxkeychain: contrib/credential/osxkeychain/git-credential-osxkeychain.o $(LIB_FILE) $(RUST_LIB) GIT-LDFLAGS
 	$(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) \
 		$(filter %.o,$^) $(LIBS) -framework Security -framework CoreFoundation
 
-- 
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